GANEX III-N Newsletter - KnowMade...having a CF3 end group with a refractive index of about 1.35, the LEE was improved by 1.5-fold, demonstrating a cost-feasible packaging technique

$Page 1: GANEX III-N Newsletter - KnowMade...having a CF3 end group with a refractive index of about 1.35, the LEE was improved by 1.5-fold, demonstrating a cost-feasible packaging technique$
Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)

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GANEX Newsletter No. 80 September 2019

III-N Technology

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GaNEX | III-N Technology Newsletter No. 80 | 2

METHODOLOGY

Each month

150+ new scientific publications

200+ new patent applications

30+ new press releases

Sources 10+ scientific journal editors

Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …

10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,

Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …

Patent database: Questel-Orbit

Selection by III-N French

experts

GANEX monthly newsletter


TABLE OF CONTENTS (clickable links to chapters)

SCIENTIFIC PUBLICATIONS ............................................................................................................................. 4

GROUP 1 - LEDs and Lighting ................................................................................................................................. 4

GROUP 2 - Laser and Coherent Light ................................................................................................................... 10

GROUP 3 - Power Electronics .............................................................................................................................. 12

GROUP 4 - Advanced Electronics and RF ............................................................................................................. 18

GROUP 5 – MEMS and Sensors............................................................................................................................ 23

GROUP 6 - Photovoltaics and Energy harvesting................................................................................................. 28

GROUP 7 - Materials, Technology and Fundamental .......................................................................................... 31

PRESS RELEASE ............................................................................................................................................ 48

PATENT APPLICATIONS ................................................................................................................................ 71


SCIENTIFIC PUBLICATIONS Selection of new scientific articles

GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)

Information selected by Benjamin Damilano and Mathieu Leroux (CRHEA-CNRS)

Ultra-wide-bandgap AlGaN homojunction tunnel

diodes with negative differential resistance School of Electrical and Computer Engineering, Georgia

Institute of Technology, Atlanta, Georgia 30332, USA

School of Electrical, Computer, and Energy Engineering,

Arizona State University, Tempe, Arizona 85287, USA

Applied Physics Letters

https://doi.org/10.1063/1.5113503

The power efficiencies of state-of-the-art AlxGa1-xN

deep-ultraviolet (UV) emitters operating in the

<300 nm wavelength region are currently limited to a

few percent in part due to limitations in the series

and contact resistance which result in excessive drive

voltages. AlxGa1-xN tunnel contacts and tunnel

junctions in deep-UV devices are a promising route

toward increasing these efficiencies by improving the

contact resistances, hole injection, and reducing

optical absorption by removing undesirable p-GaN

contact layers. However, due to doping inefficiencies,

standalone tunnel diodes have not been realized in

the form of homojunction AlxGa1-xN. In this work,

AlxGa1-xN (0.19 ≤ x ≤ 0.58) homojunction tunnel

diodes are fabricated with high reverse bias current

densities, and one device with x = 0.19 demonstrates

a negative differential resistance at ∼2.4 V. AlxGa1-

xN p++/n++/n tunnel diodes are compared to

reference p++/i/n diodes to provide clarity about the

role of tunneling conduction vs leakage conduction.

Transmission electron microscopy verifies that heavy

doping does not result in visible defects such as Mg

precipitates and allows for subsequent epitaxy,

critical for buried tunnel junction structures.

Increasing the bandgap energy of AlxGa1-xN for

higher Al content tunnel junctions decreases the

tunnel current, but still allows sufficient conduction

necessary for future improvements in deep UV

emitter efficiencies.

Challenges for reliable internal quantum efficiency

determination in AlGaN-based multi-quantum-well

structures posed by carrier transport effects and

morphology issues OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055

Regensburg, Germany

Institut für Festkörperphysik, Technische Universität Berlin,

Hardenbergstr. 36, 10623 Berlin, Germany

Institut für Halbleitertechnik, TU Braunschweig, Hans-

Sommer-Straße 66, 38106 Braunschweig, Germany

Journal of Applied Physics

https://doi.org/10.1063/1.5100498

We report on a systematic study of the

determination of the internal quantum efficiency

(IQE) in AlGaN-based multiple-quantum-well (MQW)

structures using different optical evaluation

methodologies and experimental conditions, in order

to derive a standard set of measurement conditions

for reliable IQE determination. Several potential

sources of error that may distort the IQE obtained by

optical measurements are discussed, such as carrier

transport effects, excitation conditions failing to fulfill

ideal resonance conditions, and morphology issues. A

series of nominally identical AlGaN-based MQW

structures is grown on an AlGaN layer separated by

an AlN interlayer of varying thickness. The MQW

structures are studied both by resonant and

quasiresonant photoluminescence spectroscopy, and

IQEs are determined via different commonly

employed methods. The obtained values are shown

to be significantly affected by the employed

excitation conditions, as well as the evaluation

techniques. In addition, growth morphology issues

and carrier transport effects need to be considered in

the interpretation of the measured data, with the

latter being investigated in greater detail. The results

emphasize the need for an appropriate choice of

both experimental conditions and evaluation

methodology in order to extract reliable and

comparable IQE values.

https://doi.org/10.1063/1.5113503

https://doi.org/10.1063/1.5100498


Review of encapsulation materials for AlGaN-based

deep-ultraviolet light-emitting diodes UV Craftory Co., Ltd., 2-305, Fujimidai 2-7-2, Chikusa-ku,

Nagoya 464-0015, Japan

Photonics Research

https://doi.org/10.1364/PRJ.7.000B55

This paper reviews and introduces the techniques for

boosting the light-extraction efficiency (LEE) of

AlGaN-based deep-ultraviolet (DUV: 𝜆<300 nm)

light-emitting diodes (LEDs) on the basis of the

discussion of their molecular structures and optical

characteristics, focusing on organoencapsulation

materials. Comparisons of various fluororesins,

silicone resin, and nonorgano materials are

described. The only usable organomaterial for

encapsulating DUV-LEDs is currently considered to be

polymerized perfluoro(4-vinyloxy-1-butene) (p-BVE)

terminated with a ─CF3 end group. By forming

hemispherical lenses on DUV-LED dies using p-BVE

having a ─CF3 end group with a refractive index of

about 1.35, the LEE was improved by 1.5-fold,

demonstrating a cost-feasible packaging technique.

Effect of quantum barrier composition on electro-

optical properties of AlGaN-based UVC light

emitting diodes Institute of Solid State Physics, Technische Universität

Berlin, Hardenbergstraße 36, 10623 Berlin, Germany

Ferdinand-Braun-Institut, Leibniz-Institut für

Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489

Berlin, Germany

Semiconductor Science and Technology

https://doi.org/10.1088/1361-6641/ab2c1a

The height of the barrier around the AlGaN quantum

well has a strong impact on the external quantum

efficiency of UVC light emitting diodes (LEDs) as it

affects the carrier confinement, the polarization

fields, and the injection efficiency as well as the

optical polarization and emission profile of the

emitted light. The electro-optical properties such as

emission wavelength, optical polarization, and light

output power of AlGaN multiple quantum well

(MQW) LEDs emitting around 270 nm with Al mole

fraction in the Al x Ga1−x N barriers between x = 55%

and x = 76% are investigated by electroluminescence

measurements. In order to analyze the experimental

results, 6-band kcenterdotp method-based

simulations as well as single band Schrödinger-

Poisson drift-diffusion simulations have been

conducted. It was found that for the same current

density of 100 A cm−2 the on-wafer emission power

reaches a maximum for an Al mole fraction of x = 67%

in the Al x Ga1−x N barrier of the Al0.53Ga0.47N

MQW (0.84 mW at 40 mA). Furthermore, the

emission wavelength decreases and the fraction of

transverse-electric polarized light emission increases

with increasing Al mole fraction in the barrier. This is

consistent with drift-diffusion and kcenterdotp

simulations, attributing the changes of the emission

power primarily to changes in charge carrier injection

and electrical confinement in the quantum wells

rather than to changes in the optical polarization and

light extraction.

Enhancing the light extraction efficiency of AlGaN

LED with nanowire photonic crystal and graphene

transparent electrode College of Information Science & Electronic Engineering,

Provincial Key Laboratory of Micro-Nano Electronics and

Smart System, Zhejiang University, Hangzhou 310027,

China

Ningbo Research Institute, Zhejiang University, Ningbo

315100, China

Superlattices and Microstructures

https://doi.org/10.1016/j.spmi.2019.106216

The performance of AlGaN deep ultraviolet(UV) light

emitting diodes(LEDs) has been limited by the

extremely low light extraction efficiency(LEE), which

is due to the severe light absorption by metal

electrode and unique transverse magnetic

polarization. Here, we propose an ordered nanowire

array structure UV-LEDs with transparent graphene

electrode. By using the finite-difference time domain

simulation, the relationship between LEE and

different nanowire structures (including ordered and

disordered nanowires array) was studied. We

demonstrate that ordered nanowire arrays are better

than disordered nanowires in improving the LEE. A

high LEE about 80% can, in principle, be expected

from top surface with optimized nanowire radius and

spacing. In addition, by studying the distribution of

electric field intensity on the side and top of UV-LEDs


https://doi.org/10.1088/1361-6641/ab2c1a



with graphene electrode and Ni/Au electrode, we

show that the graphene electrode can reduce the

absorption of ultraviolet light and improve LEE more

effectively than the conventional Ni/Au electrode.

This proposed structure could be a promising

candidate for high light extraction efficiency UV-LEDs.

Deep ultraviolet light-emitting diodes based on a

well-ordered AlGaN nanorod array Research and Development Center for Solid State Lighting,

Institute of Semiconductors, Chinese Academy of Sciences,

Beijing 100083, China

Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,


Beijing Engineering Research Center for the 3rd Generation

Semiconductor Materials and Application, Beijing 100083,

China

State Key Laboratory of Solid-State Lighting, Beijing

100083, China

Photonics Research


The nanorod structure is an alternative scheme to

develop high-efficiency deep ultraviolet light-emitting

diodes (DUV LEDs). In this paper, we first report the

electrically injected 274-nm AlGaN nanorod array

DUV LEDs fabricated by the nanosphere lithography

and dry-etching technique. Nanorod DUV LED devices

with good electrical properties are successfully

realized. Compared to planar DUV LEDs, nanorod

DUV LEDs present >2.5 times improvement in light

output power and external quantum efficiency. The

internal quantum efficiency of nanorod LEDs

increases by 1.2 times due to the transformation of

carriers from the exciton to the free electron–hole,

possibly driven by the interface state effect of the

nanorod sidewall surface. In addition, the nanorod

array significantly facilitates photons escaping from

the interior of LEDs along the vertical direction,

contributing to improved light extraction efficiency. A

three-dimensional finite-different time-domain

simulation is performed to analyze further in detail

the TE- and TM-polarized photon extraction

mechanisms of the nanostructure. Our results

demonstrate the nanorod structure is a good

candidate for high-efficiency DUV emitters.

Stable and efficient transfer-printing including repair

using a GaN-based microscale light-emitting diode

array for deformable displays Korea Photonics Technology Institute, Photonic Device

Research Center, 124, Cheomdanventure-ro, Buk-gu,

Gwangju, 61007, Republic of Korea

Chonnam National University, Optoelectronics

Convergence Research Center, 77, Yongbong-ro, Buk-gu,

Gwangju, 61186, Republic of Korea

Kyungpook National University, Mechanical Engineering,

80, Daehak-ro, Buk-gu, Daegu, 41566, Republic of Korea

Scientific Reports

https://doi.org/10.1038/s41598-019-47449-1

GaN-based microscale light-emitting diodes (μLEDs)

are reported for assembly into deformable displays

and repair systems. A stamp-imprinting method that

enables large area assembly without spatial limitation

is involved in the system, and a selective pick-up

method is presented that includes a method for

removing detected defective chips through micro-

pulsed laser scanning. The photosensitive functional

material, which is an accepted layer for the stable

imprinting of chips, is determined by controlling the

adhesion. In addition, selective pick-up and adhesion-

controlled functional materials allow the

implementation of defect-free displays through two

pick-and-place cycles. Displays and related systems

fabricated with this method can offer interesting

optical and electrical properties.

Common-anode LED on a Si substrate for beyond

15 Gbit/s underwater visible light communication Department of Communication Science and Engineering,

Key Laboratory for Information Science of Electromagnetic

Waves (MoE), Fudan University, Shanghai 200433, China

National Institute of LED on Silicon Substrate, Nanchang

University, Nanchang 330096, China

Photonics Research

https://doi.org/10.1364/PRJ.7.001019

Visible light communication based on light-emitting

diodes (LEDs) has become a promising candidate by

providing high data rates, low latency, and secure

communication for underwater environments. In this

paper, a self-designed common-anode GaN-based

five-primary-color LED (RGBYC LED) on a Si substrate

is proposed and fabricated. The design of a common


https://doi.org/10.1038/s41598-019-47449-1

https://doi.org/10.1364/PRJ.7.001019


anode is used to mitigate the saturation effect for a

low-frequency component. Additionally, compared

with commercially available LEDs that suffer from

nonlinearity distortion, applying the designed LED can

provide much better and broader linearity according

to the measurement results. Therefore, the

modulation depth and system performance can be

further improved to implement a high-speed

underwater visible light communication (UVLC)

system. There is no nonlinearity compensation

algorithm applied due to the good linearity of the

proposed LED; thus, the offline digital signal

processing is simplified. We experimentally

demonstrate 14.81 Gbit/s 64 quadrature amplitude

modulation (QAM)-discrete multitone (DMT) and

15.17 Gbit/s bit-loading-DMT transmissions through a

1.2-m-long underwater channel based on the

proposed RGBYC LED with an intrasymbol frequency-

domain averaging channel estimation and zero-

forcing equalization. As far as we know, this is the

highest data rate for an LED-based UVLC system.

Quantum Efficiency Enhancement Depending on the

Thickness of p-GaN Spacer Layer in Localized Surface

Plasmon-Enhanced Near-Ultraviolet Light-Emitting

Diodes by Using Colloidal Silver Nanoparticles Advanced Photonics Research Institute, Gwangju Institute

of Science and Technology, Gwangju 61005, South Korea

Department of Emerging Materials Science, Daegu

Gyeongbuk Institute of Science and Technology, Daegu

42988, South Korea

School of Materials Science and Engineering, Gwangju

Institute of Science and Technology, Gwangju 61005, South

Korea

Department of Nanobio Materials and Electronics,

Gwangju Institute of Science and Technology, Gwangju

61005, South Korea

ECS J. Solid State Sci. Technol.

https://doi.org/10.1149/2.0042001JSS

We demonstrated the dependence on thickness of p-

GaN spacer layer in the localized surface plasmons

(LSPs)-enhanced near-ultraviolet light-emitting

diodes (NUV-LEDs) by pneumatic spray process using

colloidal silver (Ag) nanoparticles (NPs). The LSPs-

enhanced NUV-LEDs with 10- and 20-nm-thick p-GaN

spacer layer showed enhanced internal quantum

efficiency (IQE) and reduced effective exciton lifetime

by introducing the colloidal Ag NPs. The IQE of LSPs-

enhanced NUV-LEDs with 10- and 20-nm-thick p-GaN

spacer layer was increased by 18.8% and 24.2%,

respectively. These results indicate that the

spontaneous emission rate is increased by LSPs-

excitons resonant coupling. However, the NUV-LEDs

with 40- and 100-nm-thick p-GaN spacer layer

showed decreased IQE and extended exciton lifetime

due to the evanescent wave property of LSPs field

from colloidal Ag NPs.

Simultaneously improve the luminous efficiency and

color-rendering index of GaN-based white-light-

emitting diodes using metal localized surface

plasmon resonance State Key Laboratory of High Performance Complex

Manufacturing, College of Mechanical and Electrical

Engineering, Central South University, Changsha Hunan,

410083, China

Semiconductor Lighting Technology Research and

Development Center, Institute of Semiconductors, Chinese

Academy of Sciences, Beijing 100083, China

College of Materials Science and Opto-Electronic

Technology, University of Chinese Academy of Sciences,


Optics Letters

https://doi.org/10.1364/OL.44.004155

With the penetration of semiconductor lighting, GaN-

based white-light-emitting diodes (WLEDs) with a

high color-rendering index (CRI) and simultaneous

high luminous efficiency (LE) are required, especially

for high-quality indoor lighting. Here, by adopting

metal nanoparticles (Ag and Au NPs) into hybridized

color conversion material composed of broadband

LuAG:Ce phosphor and narrowband CdSe/ZnS red

quantum dots, we have fabricated AgAu-WLEDs with

simultaneously increased LE (12% increment at

40 A/cm2) and CRI (maximum of 94.5), and

decreased correlated color temperature (CCT, from

CCT=6000 K to = 4800 K), compared with WLEDs

without metal NPs. This improved performance of

WLEDs is ascribed to increased color conversion

efficiency brought from localized surface plasmon

resonance and thus a strong resonant light scattering

effect from the incorporated metal NPs. We believe

the approach reported in this work will find its

application in GaN WLEDs, thus advancing the

https://doi.org/10.1149/2.0042001JSS

https://doi.org/10.1364/OL.44.004155


development of high-efficiency and quality

semiconductor lighting.

Design and Characterization of Micro-LED Matrix

Display With Heterogeneous Integration of GaN and

BCD Technologies GLOBALFOUNDRIES, Singapore 738406. He is now with AI

Singapore, Singapore 117602

Engineering Product Development (EPD), Singapore

University of Technology and Design, Singapore 487372

IEEE Transactions on Electron Devices

https://doi.org/10.1109/TED.2019.2933552

Micro-light-emitting diodes (μLEDs) are

semiconductor devices that have been shown to have

higher luminous efficacy, higher contrast ratio, and

higher energy efficiency than existing mainstream

technologies based on liquid crystals or organic LEDs

(OLEDs). Portable display applications such as

wearable devices and head-up display are some of

the interesting applications of μLED displays.

However, this technology has not yet been mass-

produced for commercial devices due to process

yields, costs, and manufacturability issues. This article

presents a novel technology for the heterogeneous

integration of a μLED matrix display with bipolar

complementary metal-oxide-semiconductor (CMOS)

DMOS (BCD) circuits that could improve

manufacturability by eliminating the need for a

dedicated bond stack in the bump-bonding process.

To validate the concept, custom high-performance, 2-

D arrays of parallel-addressed GaN blue μLEDs

matrices were fabricated. The individual μLED pixel

diameters are 20 and 50 μm, respectively, and the

overall dimension of the array is 650 μm². In addition,

a μLED display driver-integrated circuit (IC) with a

compact size of 3x4.4 mm² has been designed,

implemented, and verified experimentally for the

μLED matrices. Measured output optical power-

forward bias current-forward bias voltage (P-I-V)

curves of the individual μLED pixel are shown. The

4x4 μLED matrix has also been successfully driven

using active-matrix driving and display pictures to

demonstrate the function of active-matrix driving are

presented.

Cathodoluminescence of 2-inch Ultraviolet-Light-

Source Tube Based on the Integration of AlGaN

Materials and Carbon Nanotubes Field Emitters Department of Physics, Faculty of Science, Beni-Suef

University, Beni-Suef 62511, Egypt

Department of Materials Science and Engineering,

Chonnam National University, Gwangju 61186, Republic

of Korea

Department of Nanotechnology and Advanced Materials

Engineering, Sejong University, Seoul 05006, Republic of

Korea

SBK Materials Co., Gwangju 61186, Republic of Korea

Optoelectronic Convergence Research Center & School

of Chemical Engineering, Chonnam National University,

Gwangju 61186, Republic of Korea

Optoelectronic Convergence Research Center &

Department of Physics, Chonnam National University,

Gwangju 61186, Republic of Korea

Journal of Materials Chemistry C

https://doi.org/10.1039/C9TC03365C

High efficiency and mass-scale production ultraviolet

(UV) light sources have come to be a basic

requirement for various applications, and as such

have attracted considerable technological interest.

Here, a flat 2-inch UV-light-source tube-based triode

structure operating at 330 nm with a pulse-scan

mode was achieved by integrating the AlGaN/GaN

MQW heterostructure as a cathodoluminescence (CL)

layer and the carbon nanotube (CNT) field emitters.

The AlGaN/GaN MQW heterostructure CL layer was

grown on a high-quality 2-inch AlN/sapphire template

through metal-organic chemical vapor deposition.

The CNT emitters were fabricated on metal substrate

using a cost-effective print screen method. The

advantages of these emitters include their high stable

emission efficiency for large-scale production, cold

emission nature, controllable emission by the electric

field, and environmentally friendly nature. This

promising and effective integration demonstrates an

output power of 590 mW and a power efficiency of

2.45% with a low consumption energy of 24W (anode

current 3 mA; anode voltage 8 kV) under pulse-scan

mode. This work is the first step toward realizing

future mass-scale and high efficiency UV light source

tubes over a wide range of wavelengths.

https://doi.org/10.1109/TED.2019.2933552

https://doi.org/10.1039/C9TC03365C


Study of efficient semipolar (11-22) InGaN green

micro-light-emitting diodes on high-quality (11-22)

GaN/sapphire template Materials Department, University of California, Santa

Barbara, CA 93106, USA

Institute of Nano Optoelectronics Research and

Technology, Universiti Sains Malaysia, 11800 USM, Penang,

Malaysia

Department of Electrical and Computer Engineering,

University of California, Santa Barbara, CA 93106, USA

CNRS-CRHEA, Rue Bernard Gregory, 06560 Valbonne,

France

Optics Express

https://doi.org/10.1364/OE.27.024154

We investigated the electrical and optical

performances of semipolar (11-22) InGaN green

µLEDs with a size ranging from 20 × 20 µm2 to 100 ×

100 µm2, grown on a low defect density and large

area (11-22) GaN template on patterned sapphire

substrate. Atom probe tomography (APT) gave

insights on quantum wells (QWs) thickness and

indium composition and indicated that no indium

clusters were observed in the QWs. The µLEDs

showed a small wavelength blueshift of 5 nm, as the

current density increased from 5 to 90 A/cm2 and

exhibited a size-independent EQE of 2% by sidewall

passivation using atomic-layer deposition, followed

by an extremely low leakage current of ~0.1 nA at −5

V. Moreover, optical polarization behavior with a

polarization ratio of 40% was observed. This work

demonstrated long-wavelength µLEDs fabricated on

semipolar GaN grown on foreign substrate, which are

applicable for a variety of display applications at a

low cost.

Emission dynamics of GaN-based blue resonant-

cavity light-emitting diodes Department of Electronic Engineering, Laboratory of

Micro/Nano-Optoelectronics, School of Electronic Science

and Engineering, Xiamen University, Xiamen 361005, China

State Key Laboratory of Optoelectronic Materials and

Technologies and School of Physics, Sun Yat-Sen

University, Guangzhou 510275, China

Suzhou Institute of Nano-tech and Nano-bionics, Chinese

Academy of Sciences, Suzhou 215123, China

Department of Photonics and Institute of Electro-Optical

Engineering, National Chiao Tung University, Hsinchu 300,

Taiwan

Department of Electrical Engineering and Computer

Sciences and TBSI, University of California at Berkeley,

Berkeley, CA 94720, USA

Journal of Luminescence

https://doi.org/10.1016/j.jlumin.2019.116717

We fabricated GaN-based blue resonant-cavity light-

emitting diodes (RCLEDs) by inserting InGaN quantum

well (QW) active region between two dielectric

distributed Bragg reflectors (DBRs). Due to the

different gain enhancement factors in a single device,

multi-longitudinal modes were observed and tuned

with changing the injection current density: pure-

blue (PB) at low current density, violet-blue (VB) at

intermediate current density, and PB again at high

current density. The variation of emission spectra is

explained by the competition between band-filling

effect and self-heating effect.

https://doi.org/10.1364/OE.27.024154

https://doi.org/10.1016/j.jlumin.2019.116717


GROUP 2 - Laser and Coherent Light Group leader: Bruno Gayral (CEA)

Information selected by Knowmade

Single transverse mode operation of GaN-based

vertical-cavity surface-emitting laser with

monolithically incorporated curved mirror Sony Corporation, Atsugi, Kanagawa 243-0014, Japan

Applied Physics Express

https://doi.org/10.7567/1882-0786/ab3106

We report single transverse mode operation of a blue

GaN-based vertical-cavity surface-emitting laser

(GaN-VCSEL) with a monolithically incorporated

curved mirror. For a device with a 4 μm current

aperture diameter and a curved mirror with a radius

of curvature (ROC) of 51 μm, single transverse mode

operation was confirmed up to an output power of

3.2 mW under continuous wave operation at 20 °C.

For a device with a smaller ROC of 31 μm, multi

transverse mode operation was confirmed, indicating

that the transverse mode can be controlled by the

cavity design of such GaN-VCSELs.

Demonstration of blue semipolar (202̲1)̲ GaN-based

vertical-cavity surface-emitting lasers Materials Department, University of California, Santa




Optics Express

https://doi.org/10.1364/OE.27.023707

We successfully demonstrated an electrically injected

blue(202̲1)̲semipolar vertical-cavity surface-emitting

laser with a 5λ cavity length, an ion implanted

aperture, and a dual dielectric DBR design. The peak

power under pulsed operation was 1.85 mW, the

threshold current was 4.6 kA/cm2, and the

differential efficiency was 2.4% for the mode at 445

nm of a device with a 12 µm aperture. Lasing was

achieved up to a 50% duty cycle and the thermal

impedance was estimated to be 1800 K/W. The lasing

emission was found to be 100% plane polarized along

the a-direction.

Realization of thin-film m-plane InGaN laser diode

fabricated by epitaxial lateral overgrowth and

mechanical separation from a reusable growth

substrate Materials Department, University of California, Santa

Barbara, California 93106, USA


University of California, Santa Barbara, California 93106,

USA

Department of Engineering and Architecture, University of

Trieste, via A.Valerio 10, 34127 Trieste, Italy

Optics Express

https://doi.org/10.1364/OE.27.024717

A nonpolar edge emitting thin film InGaN laser diode

has been separated from its native substrate by

mechanical tearing with adhesive tape, combining

the benefits of Epitaxial Lateral Overgrowth (ELO) and

cleavability of nonpolar GaN crystal. The essence of

ELO is mainly to weakening strength between native

substrate and the fabricated laser device on top of it.

We report a 3 mm long laser bar removed from its

native GaN substrate. We confirmed edge emitting

lasing operation after cleaving facets on a separated

thin bar. Threshold current density of the laser was

measured to be as low as 2.15 kA/cm2.

Self-injection locking efficiency of a UV Fabry–Perot

laser diode OEwaves Inc., 465 North Halstead Street, Suite 140,

Pasadena, California 91107, USA

Jet Propulsion Laboratory, California Institute of

Technology, 4800 Oak Grove Drive, Pasadena, California

91109-8099, USA


University of California at Riverside, 900 University Ave.,

Riverside, California 92521, USA

Optics Letters

https://doi.org/10.1364/OL.44.004175

In this Letter, we have studied the performance of a

gallium nitride 370 nm Fabry–Perot laser diode self-

injection locked via a high quality (𝑄-) factor

magnesium fluoride whispering gallery mode (WGM)

https://doi.org/10.7567/1882-0786/ab3106

https://doi.org/10.1364/OE.27.023707

https://doi.org/10.1364/OE.27.024717

https://doi.org/10.1364/OL.44.004175


resonator and show that the state of locking strongly

depends on frequency detuning between the internal

laser cavity and the resonator modes. Optimizing the

detuning, we were able to observe monochromatic

laser emission with a sub-100 kHz linewidth. The 𝑄-

factor of the resonator measured in this regime

exceeded 109.

Thermal Design Considerations for III-N Vertical-

Cavity Surface-Emitting Lasers Using Electro-Opto-

Thermal Numerical Simulations School of Electrical and Computer Engineering, Georgia

Institute of Technology, Atlanta, GA 30332 USA

IEEE Journal of Quantum Electronics

https://doi.org/10.1109/JQE.2019.2937991

III-N VCSELs undergo severe self-heating which limits

the output optical power. This makes thermal

management a critical design consideration. The

three most common VCSEL structures (hybrid VCSELs,

flip-chip VCSELs and ELOG VCSELs) have been studied

using advanced self-consistent electro-opto-thermal

numerical simulations. The key geometric and

material parameters affecting the thermal resistance

of these devices have been identified. Our

simulations suggest that some of the proposed

solutions and design modifications can increase the

maximum optical output power by as much 100%.

This manuscript also describes the correct method of

using numerical simulation in device design—to

predict trends and isolate the key factors affecting

device performance.

High-efficiency, yellow-light Dy3+-doped fiber laser

with wavelength tuning from 568.7 to 581.9 nm Department of Electronic Engineering, Xiamen University,

Xiamen 361005, China

Optics Letters

https://doi.org/10.1364/OL.44.004423

We report, to the best of our knowledge, the first

demonstration of a wavelength-tunable and highly

efficient Dy3+-doped fiber laser operating in the

yellow spectral region. A 2-m-long Dy3+:ZBLAN fiber

pumped by a 447-nm GaN laser diode provides a

strong down-conversion gain around 575 nm. A fiber

end-facet mirror and a visible reflective grating in the

Littrow configuration construct the resonant cavity

and introduce the wavelength tunability. A stable

yellow laser with a <0.05−nm narrow linewidth is

achieved and continuously tuned from 568.7 nm to

581.9 nm, covering more than half of the yellow

spectral range. The slope efficiency is as high as

34.9%, and the maximum output power is 142 mW at

576.44 nm, which is 13 times higher than previously

reported. It is, to the best of our knowledge, the

highest power and conversion efficiency of a yellow-

light Dy3+-doped fiber laser with wavelength

tunability.

Performance improvement of InGaN-based laser

grown on Si by suppressing point defects Key Laboratory of Nano-devices and Applications, Suzhou

Institute of Nano-Tech and Nano-Bionics (SINANO),

Chinese Academy of Sciences (CAS), Suzhou 215123, China

University of Science and Technology Beijing, Beijing

100083, China

School of Nano Technology and Nano Bionics, University of

Science and Technology of China, Hefei 230026, China

Vacuum Interconnected Nanotech Workstation, SINANO,

CAS, Suzhou 215123, China

Optics Express

https://doi.org/10.1364/OE.27.025943

High performance InGaN-based laser diodes (LDs)

monolithically grown on Si is fundamentally

interesting and highly desirable for photonics

integration on Si platform. Suppression of point

defects is of crucial importance to improve the device

performance of InGaN-based LDs grown on Si. This

work presents a detailed study on the impact of point

defects, such as carbon (C) impurities and gallium

vacancies (VGa), on the device characteristics of

InGaN-based LDs grown on Si. By suppressing the

VGa-related defect within the waveguide layers,

reducing the thermal degradation of InGaN-based

quantum wells, and controlling the C impurity

concentrations within the thick p-type cladding

layers, the as-fabricated InGaN-based LDs grown on

Si exhibited a significantly reduced threshold current

density of 2.25 kA/cm2 and an operation voltage of

4.7 V..

https://doi.org/10.1109/JQE.2019.2937991

https://doi.org/10.1364/OL.44.004423

https://doi.org/10.1364/OE.27.025943


GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)

Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)

Experimental determination of impact ionization

coefficients of electrons and holes in gallium nitride

using homojunction structures Department of Electrical Engineering, Stanford University,

Stanford, California 94305, USA


University of California, Davis, California 95616, USA


https://doi.org/10.1063/1.5099245

In this study, we experimentally determined the

impact ionization coefficients of GaN using

homoepitaxially grown p-n diodes with avalanche

capability. The extracted hole impact ionization

coefficient is obtained as β(E) = 4.39 × 106 exp

(−1.8 × 107/E) cm−1, and the electron impact

ionization coefficient is obtained as α(E) = 2.11 × 109

exp (−3.689 × 107/E) cm−1. This study also presents

the temperature dependence of impact ionization

coefficients in GaN. The results presented in this

experimental study are an important contribution to

the database on the material properties of GaN,

which will enable more accurate prediction of the

avalanche in GaN devices.

Leakage mechanism of quasi-vertical GaN Schottky

barrier diodes with ultra-low turn-on voltage Key Laboratory of Wide Band Gap Semiconductor

Materials and Devices, School of Microelectronics, Xidian

University, Xi'an 710071, People's Republic of China

Applied Physics Express

https://doi.org/10.7567/1882-0786/ab3297

The leakage mechanism of quasi-vertical GaN

Schottky barrier diodes (SBDs) with ultra-low turn-on

voltage has been investigated. By using a tungsten

anode, the turn-on voltage is 0.39 V and the average

breakdown electric field is above 1 MV cm−1. Under

low reverse bias, the thermionic emission is

dominated. When the reverse bias increases to a

certain value, the increased electric field promotes

the electron hopping along the threading dislocation

in the bulk GaN layers, and variable range hopping

(VRH) becomes the main leakage current mechanism.

The leakage difference between tungsten-anode and

nickel-anode SBDs is reduced to one order of

magnitude due to the VRH mechanism.

Investigation of Dynamic IOFF Under Switching

Operation in Schottky-Type p-GaN Gate HEMTs Department of Electronic and Computer Engineering, The

Hong Kong University of Science and Technology, Hong

Kong


https://doi.org/10.1109/TED.2019.2930315

In this paper, systematic characterization and the

corresponding suppression strategies of dynamic

OFF-state leakage current ( IOFF ) in Schottky-type p-

GaN gate high-electron-mobility transistors (HEMTs)

are presented based on fast pulsed I – V

measurement and consecutive switching

measurement. It is found that the high IOFF under

dynamic pulse mode without hole injection is a result

of the reduced voltage blocking capabilities (both

lateral and vertical) with weaker trapping effect in

the buffer, and the dynamic IOFF induced by ON-

state hole injection is caused by further increased

lateral conductivity through the buffer from source to

drain. The corresponding behaviors under continuous

waveforms with different switching conditions are

analyzed to identify effective approaches for the

suppression of dynamic IOFF in practical switching

operations. A higher temperature is shown to be

beneficial to the reduction of the dynamic IOFF

induced by ON-state hole injection. To completely

eliminate the dynamic IOFF caused by ON-state hole

injection and minimize the OFF-state power

consumption in practical power switching

applications, a sufficiently large negative OFF-state

gate bias (e.g., VGS,OFF≤−3 V) is recommended in the

gate driver turn-off voltage design for the Schottky-

type p-GaN gate HEMTs.

https://doi.org/10.1063/1.5099245

https://doi.org/10.7567/1882-0786/ab3297

https://doi.org/10.1109/TED.2019.2930315


A >3 kV/2.94 mΩ ·cm2 and Low Leakage Current

with Low Turn-on Voltage Lateral GaN Schottky

Barrier Diode on Silicon Substrate with Anode

Engineering Technique Key Laboratory of Wide Band Gap Semiconductor

Materials and Devices, School of Microelectronics, Xidian

University, Xi’an 710071, P. R. China.

Science and Technology on Monolithic Integrated Circuits

and Modules Laboratory, Nanjing Electronic Devices

Institute, Nanjing 210016, China.

IEEE Electron Device Letters

https://doi.org/10.1109/LED.2019.2933314

In this letter, we report on demonstrating high-

performance lateral GaN Schottky barrier diode (SBD)

on silicon substrate with low turn-on voltage (Von),

high breakdown voltage (BV) with low reverse

leakage current (IR), and high power figure of merit

(P-FOM) through anode engineering technique.

Lateral GaN SBD with anode-cathode distance (LAC)

of 25 μm demonstrates a Von = 0.38 V, a BV of >3 kV

at a IR of 10 μA/mm and differential specific ON-

resistance (Ron,sp) of 2.94 mΩ ·cm2, yielding a high

P-FOM of more than 3 GW/cm2. To the best of our

knowledge, this P-FOM is the highest value among all

the GaN SBDs on any substrates. Combining with 5 A

forward current (IF) and reverse BV > 2 kV of a large

periphery device with perimeter of 20 mm, GaN SBD

with anode engineering technique shows its great

promise for next generation power electronics.

ON-Resistance in Vertical Power FinFETs Center for Power Electronics Systems, Virginia Polytechnic

Institute and State University, Blacksburg, VA, USA

Microsystems Technology Laboratories, Massachusetts

Institute of Technology, Cambridge, MA, USA


https://doi.org/10.1109/TED.2019.2928825

This paper presents the first analytical model for the

ON-resistance ( RON ) in vertical power FinFETs. The

model allows to extract the channel mobility and

series resistance and to separate the current

conduction through the bulk fin channel and the

accumulation-mode metal–oxide–semiconductor

(MOS) channel. The model was validated by

experiments and simulations. The extracted series

resistance was verified by measuring a diode

fabricated in the same wafer with the FinFETs. At the

same time, simulations using the extracted channel

mobility and series resistance agreed well with the

experiments. The model was then used to analyze a

1200 V GaN vertical power FinFET. The main RON

component was identified to be from the drift layer

and the substrate, while the gate-modulated channel

resistance only accounts for ~13% of the total device

RON . Our model enables parameter extraction from

the dc characteristics of a single device, and

therefore, provides a fast and easy way to

understand, analyze, and design vertical power

FinFETs. Our model can also be adjusted to allow for

fast and accurate parameter extraction in other

power transistors with a vertical gate-modulated

channel, such as trench MOSFETs.

Investigation of the nanochannel geometry

modulation on self-heating in AlGaN/GaN Fin-

HEMTs on Si State Key Discipline Laboratory of Wide Band-Gap

Semiconductor Technology, School of Microelectronics,

Xidian University, Xi'an 710071, People's Republic of China

School of Advanced Materials and Nanotechnology, Xidian

University, Xi'an 710071, People's Republic of China


https://doi.org/10.1063/1.5111607

The impact of the nanochannel geometry on the

thermal performance of AlGaN/GaN Fin-HEMTs was

investigated. Structures with a larger nanochannel

space (Sfin) or a smaller nanochannel width (Wfin)

show the suppressed self-heating effect, which was

confirmed by the smaller dispersion between DC and

pulsed measurements together with the reduced

high temperature degradation of the drain current. A

closed-form expression based on the heat flow

theory was used to illustrate the coupling effect of

Wfin and Sfin, and the channel temperature was

mapped considering the different nanochannel

geometries. As Wfin and Sfin scale down

simultaneously, the nanochannel structure would

present a much lower channel temperature,

demonstrating that the heat generation dominated

by Wfin has a greater impact on the self-heating in

Fin-HEMTs.

https://doi.org/10.1109/LED.2019.2933314

https://doi.org/10.1109/TED.2019.2928825

https://doi.org/10.1063/1.5111607


Experimental Demonstration of n- and p-channel

GaN-MOSFETs toward Power IC Applications AIST-NU GaN-OIL, Akasaki Institute 4F, Nagoya, Aichi 464-

8601, Japan

Graduate School of Engineering, Nagoya University,

Nagoya 464-8603, Japan


https://doi.org/10.1149/2.0012001JSS

We report on the systematic demonstrations of the

depletion-mode p-channel and enhancement-mode

n-channel GaN metal-oxide field-effect transistors

(MOSFETs) based on homoepitaxial p-GaN substrates.

The world's first depletion-mode p-channel GaN-

MOSFET fabricated in this work shows a good Ion/Ioff

characteristic (∼104) and an effective channel hole

mobility of approximately 0.2 cm2/V·s at room

temperature. For the first time, it is proved that the

p-channel GaN-MOSFETs can work independently

without the necessity of two-dimension hole gas

(2DHG) sources of heterostructures. Meanwhile, the

maximum effective electron mobility of n-channel

GaN-MOSFETs is approximately 105 cm2/V·s. The

post deposition annealing (PDA) treatment of Al2O3

dielectrics is also verified in both n and p-channel

GaN-MOSFETs and 700°C is found to be the

optimized condition on improving the effective

hole/electron mobility. The findings in this work

provide a valuable information in the design of novel

power electronics taking advantage of p-type doped

GaN.

A Method for Obtaining the Real Off-State

Breakdown Voltage of AlGaN/GaN MIS-HEMTs in

On-Wafer Tests by Optimizing Protective Layer Engineering Research Center for Optoelectronics of

Guangdong Province, School of Electronics and

Information Engineering, South China University of

Technology, Guangzhou, China

IEEE Journal of the Electron Devices Society

https://doi.org/10.1109/JEDS.2019.2935323

We demonstrate a method for testing the real off-

state breakdown voltage ( VBD ) of AlGaN/GaN

metal–insulator-semiconductor high electron

mobility transistor (MIS-HEMTs) in on-wafer tests.

The method prevents the arcing over air at high

voltage by depositing the protective layer between

the pad electrodes of source and drain. The influence

of materials and thickness of the protective layer on

the high voltage tests of MIS-HEMTs were

investigated. We found that it is helpful to obtain the

real VBD of the devices by increasing the thickness of

the protective layer and selecting a material with a

higher critical breakdown field strength. The real VBD

of the device with a gate-to-drain spacing of 25 μm is

1164 V when 1.5 μm SiO 2 is deposited as the

protective layer, which is 141% higher than that of

the value tested in air.

Low-damage Etching for AlGaN/GaN HEMTs Using

Photo-electrochemical Reactions Research Center for Integrated Quantum Electronics

(RCIQE), Hokkaido University, Sapporo, 060-0813 Japan

IEEE Transactions on Semiconductor Manufacturing

https://doi.org/10.1109/TSM.2019.2934727

This paper describes our recent efforts to optimize

photo-electrochemical (PEC) etching for fabricating

recessed-gate aluminum gallium nitride/gallium

nitride (AlGaN/GaN) high-electron-mobility

transistors (HEMTs). Selecting the proper light

wavelength and voltage conditions enabled PEC

etching on AlGaN/GaN heterostructures to produce

smooth and flat surfaces. Self-termination

phenomena observed under optimal PEC condition

were useful for precisely controlling the etching

depth in the AlGaN layer. Two types of HEMTs, i.e.,

Schottky-gate and metal-insulator-semiconductor

(MIS)-gate, were fabricated. A recessed-gate

AlGaN/GaN structure fabricated with PEC etching

showed positive threshold voltage, and its variation

was very small with a standard deviation of only

0.019 V for the Schottky-gate HEMTs and 0.032 V for

the MIS-gate HEMTs. A recessed-gate structure with

PEC etching showed better current transport

controllability with a small subthreshold-slope than

that of planar-gate and dry-etched-gate AlGaN/GaN

structures.

https://doi.org/10.1149/2.0012001JSS


https://doi.org/10.1109/TSM.2019.2934727


Temperature-Dependent Leakage Current

Characteristics of Homojunction GaN p-i-n Rectifiers

Using Ion-Implantation Isolation School of Electrical and Computer Engineering, Georgia


Department of Material Science and Engineering, Georgia



https://doi.org/10.1109/TED.2019.2933421

We report vertical GaN p-i-n rectifiers grown on a

bulk GaN substrate. These planar GaN p-i-n rectifiers

were implemented with Schottky field plates and

buried-junction field terminations using ion

implantation as a mean of device isolation. The 1130-

μm-diameter GaN p-i-n rectifiers achieved a blocking

voltage (BV) of 1.2 kV and an ON-state current drive

of 10 A. A temperature-dependent OFF-state current

study showed that the variable-range-hopping (VRH)

conduction is dominant for devices operating at the

temperature of less than 160 K, and multistep

electron transition is responsible for the reverse-

biased leakage at higher temperature. Further study

suggested the leakage current arises from the deep

centers formed through the ion-implantation damage

that led to perimeter-dependent leakage currents in

GaN p-i-n rectifiers using ion-implanted isolation

approach.

Heavy ion irradiation effects on GaN/AlGaN high

electron mobility transistor failure at off-state Department of Mechanical Engineering, The Pennsylvania

State University, University Park, PA 16802, USA

Department of Chemistry, Princeton University, Princeton,

NJ 08540, USA

Sandia National Laboratories, PO Box 5800-1056,

Albuquerque, NM 87185, USA

Department of Materials Science and Engineering,

University of California, Irvine, CA 92697, USA

Air Force Research Laboratory, Materials and

Manufacturing Directorate, 2941 Hobson Way, Wright-

Patterson AFB, OH 45433, USA

Microelectronics Reliability

https://doi.org/10.1016/j.microrel.2019.113493

We investigate the effects of ion irradiation on

AlGaN/GaN high electron mobility electron

transistors using in-situ transmission electron

microscopy. The experiments are performed inside

the microscope to visualize the defects,

microstructure and interfaces of ion irradiated

transistors during operation and failure. Experimental

results indicate that heavy ions such as Au4+ can

create a significant number of defects such as

vacancies, interstitials and dislocations in the device

layer. It is hypothesized that these defects act as

charge traps in the device layer and the resulting

charge accumulation lowers the breakdown voltage.

Sequential energy dispersive X-ray spectroscopy

mapping allows us to track individual chemical

elements during the experiment, and the results

suggest that the electrical degradation in the device

layer may originate from oxygen and nitrogen

vacancies.

Epi-Gd2O3/AlGaN/GaN MOS HEMT on 150 mm Si

wafer: A fully epitaxial system for high power

application Department of Electrical Engineering, Indian Institute of

Technology Bombay, Mumbai 400076, India

Department of Physics, Indian Institute of Technology

Bombay, Mumbai 400076, India

Department of Electronics and Nanoengineering, Aalto

University, P. O. BOX 13500, FI-00076 AALTO, Finland

Institute of Electronic Materials and Devices, Leibniz

University Hannover, Schneiderberg 32, 30167 Hannover,

Germany


https://doi.org/10.1063/1.5109861

In this letter, we report the impact of epitaxial Gd2O3

on the electrical properties of an AlGaN/GaN high

electron mobility transistor (HEMT) grown on a

150 mm diameter Si (111) substrate. Incorporation of

epitaxial Gd2O3 grown by the molecular beam

epitaxy technique under a metal gate

(metal/Gd2O3/AlGaN/GaN) causes six orders of

magnitude reduction in gate leakage current

compared to metal/AlGaN/GaN HEMT. We observe

that epi-Gd2O3 undergoes complete structural

changes from hexagonal to monoclinic as the

thickness of the layer is increased from 2.8 nm to

15 nm. Such structural transformation is found to

have a strong impact on electrical properties

whereby the gate leakage current reaches its

minimum value when the oxide thickness is 2.8 nm.

https://doi.org/10.1109/TED.2019.2933421

https://doi.org/10.1016/j.microrel.2019.113493

https://doi.org/10.1063/1.5109861


We find a similar trend in the density of interface

traps (Dit) having a minimum value of

2.98 × 1012 cm−2 eV−1 for the epioxide layer of

thickness 2.8 nm. Our measurements also confirm a

significant increase in the two dimensional electron

gas (2DEG) density (∼40%) at AlGaN/GaN interface

with epioxide grown on AlGaN, thus confirming the

contribution of epitaxial lattice strain on 2DEG

modulation.

A sandwich-structured AlGaN/GaN HEMT with

broad transconductance and high breakdown

voltage State Key Laboratory of Luminescent Materials and

Devices, South China University of Science and

Technology, Guangzhou 510640, China

The school of Materials Science and Engineering, South

China University of Science and Technology, Guangzhou

510640, China

Journal of Materials Chemistry C

https://doi.org/10.1039/C9TC03718G

This paper reports a sandwich-structured AlGaN/GaN

high electron mobility transistor (HEMT). The design

includes a bottom gate, a top field plate and an AlN

dielectric layer, which realized broad

transconductance (gate voltage operating between -3

V ~ 3 V) and high off-state breakdown voltage (620 V

@ Vg = -10 V) simultaneously. The device shows great

potential in the application of high-power electronics

with good linear characteristics.

Safe Operating Area of Polarization Super-junction

GaN HEMTs and Diodes Department of Electronic Systems Engineering, Indian

Institute of Science, Bangalore 560012, India


https://doi.org/10.1109/TED.2019.2933362

This article reports safe operating area (SOA)

assessment in polarization super-junction (PSJ)-based

GaN high-electron mobility transistor (HEMT) and

Schottky diode. The degradation physics, which limits

SOA in these devices under high-voltage and high-

current-injection conditions is presented. Trap-

induced SOA degradation and the role of PSJ in SOA

improvement are unveiled. In PSJ-field-effect

transistor (FET), the impact of PSJ length and its

position on SOA robustness are studied. The role of

self-heating and substrate effect on degradation are

discussed. PSJ diodes with different configurations of

Schottky contact are investigated. The correlation

between PSJ length and failure threshold is

discovered, besides power and field dependence of

SOA boundary. Compared with their conventional

counterparts, unique failure modes are discovered in

PSJ-based GaN HEMT and diode.

An Extraction Method for the Interface Acceptor

Distribution of GaN MOS-HEMT State Key Laboratory of Electronic Thin Films and

Integrated Devices, University of Electronic Science and

Technology of China, Chengdu 610054, China

Science and Technology on Monolithic Integrated Circuits

and Modules Laboratory, Nanjing Electronic Devices

Institute, Nanjing 210016, China


https://doi.org/10.1109/TED.2019.2936509

This article presents a method for extracting the

interface acceptor distribution of GaN metal-oxide-

semiconductor high electron mobility transistor

(MOS-HEMT) using a compact 2-dimensional electron

gas model. The presented method is capable of self-

consistently calculating the Fermi energy and the

density of the ionized interface acceptor (nit,A).

Through the presented method, the density of states

(DoS) of the interface acceptor (Dit,A) and nit,A are

obtained. Especially, the DoS of the interface

acceptor distributed close to the conductband is also

obtained. The calculated results are well supported

by the results from the ac conductance method and

the subthreshold swing (SS)-based method, thus

verifying the correctness of the presented method.

https://doi.org/10.1039/C9TC03718G

https://doi.org/10.1109/TED.2019.2933362

https://doi.org/10.1109/TED.2019.2936509


Proposal of a novel recess-free enhancement-mode

AlGaN/GaN HEMT with field-assembled structure: a

simulation study School of Information and Software Engineering, University

of Electronic Science and Technology of China,

ChengduPeople’s Republic of China

Journal of Computational Electronics

https://doi.org/10.1007/s10825-019-01383-7

A novel recess-free enhancement-mode AlGaN/GaN

high-electron-mobility transistor (HEMT) is proposed.

The device features a field-assembled structure (FAS)

consisting of one short Schottky source finger as well

as an overlying gate, which can modulate the

potential beneath the source. This structure enables

manipulation of the source barrier height and thus

modulation of the current through the reverse

source-to-drain Schottky barrier diode. According to

the analytical model and detailed simulations, the

proposed FAS–HEMT has great potential for use in

power converters, monolithic microwave integrated

circuits, and other applications.

https://doi.org/10.1007/s10825-019-01383-7


GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)

Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)

High Thermal Boundary Conductance across Bonded

Heterogeneous GaN–SiC Interfaces Collaborative Research Center, Meisei University, Hino-shi,

Tokyo 191-8506, Japan

George W. Woodruff School of Mechanical Engineering,

Georgia Institute of Technology, Atlanta, Georgia 30332,

USA

Kagami Memorial Research Institute for Materials

Science and Technology, Waseda University, Shinjuku,

Tokyo 169-0051, Japan

Department of Mechanical Engineering, The University of

Tokyo, Bunkyo, Tokyo 113-8656, Japan

School of Materials Science and Engineering, Georgia

Institute of Technology, Atlanta, Georgia 30332, USA

ACS Appl. Mater. Interfaces

https://doi.org/10.1021/acsami.9b10106

High-power GaN-based electronics are limited by

high channel temperatures induced by self-heating,

which degrades device performance and reliability.

Increasing the thermal boundary conductance (TBC)

between GaN and SiC will aid in the heat dissipation

of GaN-on-SiC devices by taking advantage of the

high thermal conductivity of SiC substrates. For the

typical growth method, there are issues concerning

the transition layer at the interface and low-quality

GaN adjacent to the interface, which impedes heat

flow. In this work, a room-temperature bonding

method is used to bond high-quality GaN to SiC

directly, which allows for the direct integration of

high-quality GaN with SiC to create a high TBC

interface. Time-domain thermoreflectance is used to

measure the GaN thermal conductivity and GaN–SiC

TBC. The measured GaN thermal conductivity is

larger than that of grown GaN-on-SiC by molecular

beam epitaxy. High TBC is observed for the bonded

GaN–SiC interfaces, especially for the annealed

interface (∼230 MW m–2 K–1, close to the highest

value ever reported). Thus, this work provides the

benefit of both a high TBC and higher GaN thermal

conductivity, which will impact the GaN-device

integration with substrates in which thermal

dissipation always plays an important role.

Additionally, simultaneous thermal and structural

characterizations of heterogeneous bonded

interfaces are performed to understand the

structure–thermal property relation across this new

type of interface.

Ultra-Wideband Dual-Mode Doherty Power

Amplifier Using Reciprocal Gate Bias for 5G

Applications School of Electrical and Electronic Engineering, University

College Dublin, Dublin 4, Ireland

IEEE Transactions on Microwave Theory and Techniques

https://doi.org/10.1109/TMTT.2019.2932977

A novel architecture to extend the bandwidth of the

Doherty power amplifier (DPA) is presented in this

article. It is illustrated that two DPA modes at

different frequency bands can be realized by simply

swapping the gate biases of the transistors without

changing the matching circuits, and hence, ultrawide

bandwidth can be achieved by using a single load

modulation network in DPA. A dual-mode DPA with

2.8-4.1-GHz bandwidth for Mode I and 2.2-2.7-

GHz/4.2-4.8-GHz bandwidth for Mode II using

commercial GaN transistors is designed and

implemented to validate the proposed architecture.

The fabricated DPA attains a measured 7.5-11.7-dB

gain and 39.2-41-dBm saturated power. 35.0%-49.7%

drain efficiency is obtained at 6-dB output power

back-off for the designed dual-mode bands. When

driven by a ten-carrier 200-MHz OFDM signal with

7.7-dB peak-to-average power ratio, the proposed

DPA achieves adjacent channel leakage ratio of better

than -50 dBc after digital predistortion at 2.5 GHz/3.5

GHz/4.5 GHz with an average efficiency of

46.0%/35.7%/33.0%. This simple configuration

provides a promising solution for 5G, where multiple

frequency bands in sub-6 GHz will be deployed.


https://doi.org/10.1109/TMTT.2019.2932977


A Directly Matched PA-Integrated K-band Antenna

for Efficient mm-Wave High-Power Generation Electrical Engineering, Chalmers University of Technology,

11248 Gothenburg Sweden

Microtechnology and Nanoscience, Chalmers University of

Technology, 11248 Gothenburg Sweden

IEEE Antennas and Wireless Propagation Letters

https://doi.org/10.1109/LAWP.2019.2937235

A K-band slot antenna element with integrated GaN

(Gallium nitride) power amplifier (PA) is presented. It

has been optimized through a circuit-EM co-design

methodology to directly match the transistor drain

output to its optimal load impedance ( Zopt=17+j46Ω

) while accounting for the over-the-air coupling

effects in the vicinity of the transition between the

PA and antenna. This obviates the need for using a

potentially lossy and bandwidth-limiting output

impedance matching network. The measured PA-

integrated antenna gain of 15 dBi with a 40% total

efficiency at 28 dBm output power agrees well with

the theoretically achievable performance targets. The

proposed element is compact ( 0.6×0.5×0.3 λ3 ), and

thus well-suited to meet the high-performance

demands of future emerging beamforming active

antenna array applications.

High-performance high electron mobility transistors

with GaN/InGaN composite channel and

superlattice back barrier State Key Discipline Laboratory of Wide Band Gap

Semiconductor Technology, School of Microelectronics,

Xidian University, No. 2 South TaiBai Road, Xi'an 710071,

China

Institute of Semiconductor, Chinese Academy of Sciences,


Jihua Laboratory, Foshan 528200, China


https://doi.org/10.1063/1.5102080

A heterostructure with a GaN/InGaN composite

channel and superlattice back barrier is proposed,

and high-performance high electron mobility

transistors (HEMTs) are achieved on it. The carriers in

the GaN/InGaN composite channel are well confined

in the “U-pattern” potential well, which

simultaneously possess high mobility, high density,

and superior confinement. As a result, the output

current density and linearity of the HEMTs are

enhanced. Moreover, the GaN/InGaN superlattice

back barrier effectively suppresses the buffer

leakage, resulting in the significant improvement in

the breakdown performance of the devices. The

results in this work demonstrate the great promise of

the devices with the GaN/InGaN composite channel

and superlattice back barrier for next generation high

power and wideband electronic applications.

Microwave Characterization of Trapping Effects in

100-nm GaN-on-Si HEMT Technology Department of Electrical, Electronic and Information

Engineering ''G. Marconi,'' University of Bologna, 40136

Bologna, Italy

IEEE Microwave and Wireless Components Letters

https://doi.org/10.1109/LMWC.2019.2933186

Trapping effects of a state-of-the-art 100-nm GaN-on-

Si high-electron mobility transistor (HEMT) process

for radio-frequency (RF) applications are

characterized for the first time. Considering an

operation with high peak-to-average power ratio

(PAPR) signals, pulsed-RF measurements give a more

direct understanding of the dynamic trap behavior

than the third-order intermodulation products (IM3).

The experimental data are used for estimating the

time constants describing the transients in the

presence of signals with different PAPRs.

Measurement of Self-Heating Temperature in

AlGaN/GaN HEMTs by Using Cerium Oxide Micro-

Raman Thermometers Groupe de Recherche en Informatique, Image,

Automatique et Instrumentation de Caen, Normandie

Université, UNICAEN, ENSICAEN, CNRS, GREYC, 14000

Caen, France

Department of Technology and Innovation, Thales Land

and Air Systems, 76520 Ymare, France

Institut d'Electronique, de Microélectronique et de

Nanotechnologie, Cité scientifique, 59652 Villeneuve

d'Ascq, France


https://doi.org/10.1109/TED.2019.2935335

A new experimental technique to characterize the

self-heating temperature of biased AlGaN/GaN high-

https://doi.org/10.1109/LAWP.2019.2937235

https://doi.org/10.1063/1.5102080

https://doi.org/10.1109/LMWC.2019.2933186

https://doi.org/10.1109/TED.2019.2935335


electron-mobility transistors (HEMTs) is presented in

this article. This method involves using micro-Raman

thermography and CeO₂ microparticles deposited on

the GaN semiconductor and the metal ohmic and

gate contacts of the AlGaN/GaN HEMTs. Thus, it

allows estimating the self-heating temperature of

these biased devices not only from the changes with

the component temperature in the phonon

frequencies but also from the linewidth of Raman

lines related to the CeO₂ microparticles. In these

conditions, the characterization of the metal surfaces

by Raman thermography becomes possible by using

these CeO₂ Raman microthermometers although the

metal material cannot be characterized directly by

Raman spectroscopy. Moreover, transparency of the

CeO₂ microparticles also permits to measure the

temperature of volumetric GaN/AlGaN layers.

Henceforth, the Raman spectroscopy is the only

technique that offers the possibility of simultaneously

measuring the self-heating temperature in the well-

defined volume in the GaN semiconductor layers, of

the semiconductor surface, the metal ohmic and gate

contacts, and the substrate of the biased

components.

Concept for Continuously Tunable Output Filters for

Digital Transmitter Architectures Institute for Microwave Engineering and Photonics,

Technische Universität Darmstadt, Darmstadt, 64283

Germany

Ferdinand-Braun-Institut, Leibniz-Institut für

Höchstfrequenztechnik, Berlin, 12489 Germany

IEEE Access

https://doi.org/10.1109/ACCESS.2019.2938041

This paper presents a novel output filter approach for

continuously frequency-tunable digital power

amplifiers, suitable for future seamless and band-less

applications in 5G, e.g. for cognitive radios (CR). The

presented tunable output filter is based on a multi-

bandstop lowpass response to regenerate the

original microwave signal at the output of the digital

amplifier stage by suppressing unwanted frequency

components. Compared to conventional tunable

bandpass solutions, it offers higher tunability, higher

linearity, good power handling capability and

moderate losses especially around the carrier

frequency. A tunable power amplifier (PA)

demonstrator consisting of a 4-stage digital GaN PA

MMIC and the novel tunable filter, is designed and

fabricated for a carrier frequency range from 1 GHz

to 3 GHz. Tunability is achieved by using commercial

barium strontium titanate (BST) varactors. Small

signal measurements were performed to evaluate

tunability and suppression capabilities of the novel

filter structure, which reveal a frequency tunability of

67% with a suppression level of at least 13 dB for the

undesired frequency components. The proposed

filter structure exhibits a linearity over the tuning

range with an OIP3 between 66 dBm to 70 dBm and

high power handling capability. Finally, the

performance analysis of the tunable PA demonstrator

shows an peak efficiency of 70%. Due to frequency

limitations of the used PA stage, the efficiency slowly

degrades to 20% at the upper frequency band edge.

Simultaneously, the output power varies between

27dBm to 31dBm.

High-Q GaN Varactors for mm-Wave Applications: A

Physics-Based Simulation Study School of Electrical Engineering and Computer Science,

Pennsylvania State University, State College, PA 16802 USA


https://doi.org/10.1109/TED.2019.2933742

Varactors, with its capacitance tunable by the applied

voltage, are enabling components for reconfigurable

RF systems. The performance of a varactor could be

characterized by its Q-factor and the capacitance

tuning ratio. In this article, we seek to develop a new

varactor with very high Q-factor and large tuning

ratio, enabling reconfigurable RF systems with large

bandwidth. There were two main innovations in

varactor diode design. One was the use of the fin

structure, in which the electrodes were placed on

two opposite sidewalls of the mesa structure instead

of one on top and the other at the bottom or next to

the mesa. This design eliminates the extrinsic series

resistance in the conventional varactor diode designs,

leading to substantially increased Q-factor. The other

was the use of a multichannel structure. The

structure was composed of multiple AlGaN/GaN

heterojunctions with high-mobility 2-D electron gas.

The high-mobility electron gas helped lowering the

intrinsic series resistance, thereby further improving

the Q-factor.


https://doi.org/10.1109/TED.2019.2933742


Semiconductor-Metal-Grating Slow Wave Amplifier

for Sub-THz Frequency Range School of Electrical Engineering, KTH Royal Institute of

Technology, 100 44 Stockholm, Sweden


https://doi.org/10.1109/TED.2019.2935312

The concept of semiconductor slow wave amplifier

aimed at sub-terahetz frequencies is studied

numerically. The scheme of the transversal amplifier

with metal grating is proposed. The requirements on

semiconductor parameters that provide positive net

amplification are given and discussed, and the choice

of GaN is explained. For the proposed device,

different regimes are studied, and the dependence of

the net amplification on device parameters is given.

One regime has high linear gain, more than 50

dB/mm. The proof-of-principle structure for the

excitation of the device in this regime is proposed

and simulated.

A Threshold Voltage Model for Charge Trapping

Effect of AlGaN/GaN HEMTs School of Electronic Science and Engineering, University of

Electronic Science and Technology of China, Chengdu

611731, China

Department of Electrical Engineering, Yale University, New

Haven, CT 06520, USA


National University of Singapore, Singapore 117576,

Singapore

National University of Singapore Suzhou Research

Institute, Suzhou 215123, China

IEEE Access


In this paper, a threshold voltage model for charge

trapping effect of AlGaN/GaN HEMTs is proposed.

The quiescent bias stresses are considered for well

modeling the current collapse critical points in pulsed

I-V curves. Moreover, the low-frequency dispersions

due to the charge trapping effect are well disposed

by using the proposed model, which are validated by

the scattering parameters (S-parameters). Also, a

trapping related parameter a is proposed in the

model, which can be conveniently used to describe

the current collapse critical points offset due to the

different acceptor energy levels of the dopants in

GaN buffer. Different from our previous threshold

voltage model, the proposed model in this paper can

accurately model the dynamic threshold voltage shift

due to the fast capture and slow emission processes.

The verifications are carried out by comparing with

the transient measured drain current. The proposed

model is also implemented into a large-signal model

for further verifications. The improved large-signal

model with the threshold voltage shift model is

verified by 0.25 lm process AlGaN/GaN HEMTs with

pulsed I-V, S-parameters, power sweep and load-pull

measurements. More accurate agreements between

measured and modeled results have been achieved in

terms of output power (Pout), gain, and power added

efficiency (PAE).

Bandwidth Enhancement of GaN MMIC Doherty

Power Amplifiers Using Broadband Transformer-

Based Load Modulation Network School of Electrical and Electronic Engineering, University

College Dublin, Dublin, Ireland

IEEE Access


In this paper, we present a bandwidth enhancement

technique for monolithic microwave integrated

circuit (MMIC) Doherty power amplifiers (DPAs) in

wireless transmitters. A broadband load modulation

network is proposed by exploiting transformers and

output-referred parasitic capacitances of the carrier

and peaking transistors of DPA. The proposed

network comprises two transformers that are used to

improve frequency response of the load impedance

presented to the carrier transistor at back-off and

extend the DPA bandwidth. The network benefits

from a unity transformation ratio and it can be

readily realized by using edge-coupled microstrip

transmission lines. Optimal coupling coefficients of

the two transformers are determined based on

bandwidth and insertion loss considerations. A proof-

of-concept DPA is implemented in a 0.25- $\mu

\text{m}$ GaN MMIC process. It achieves 35–36 dBm

output power, 42.8–48.7% drain efficiency at peak

power and 24.4–31.6% at 6-dB back-off, over 4.5–6.0

GHz bandwidth. When excited by a 100-MHz 64-QAM

signal with 8 dB peak-to-average power ratio (PAPR),

the DPA exhibits 29.3 dBm average output power and

28.4% average drain efficiency, while the error vector

https://doi.org/10.1109/TED.2019.2935312




magnitude (EVM) is −30.5 dB (3%) without any

predistortion.

Characterization and analysis of low-noise GaN-

HEMT based inverter circuits Department of Electronics and Communication

Engineering, Kalyani Government Engineering College,

Nadia, India

Microsystem Technologies

https://doi.org/10.1007/s00542-019-04592-z

In this work, the authors have propounded a novel

Gallium Nitride High Electron Mobility Transistor

(GaN-HEMT) structure and have analyzed its DC, RF

and noise performance parameters. The DC

characteristics reveal a high ON-state current in the

order of 10−2 A/mm complemented by a near ideal

sub-threshold swing of 70 mV/decade. High values of

cut-off frequency (ft = 126 GHz) and maximum

oscillation frequency (fmax = 224 GHz) are obtained

which indicate high frequency range of operation. A

minimum noise figure in the order of 10−5 dB has

been achieved for lower frequencies of operation

that remains considerably low even beyond 30 GHz

(1.7 dB at 45 GHz and 4 dB at 100 GHz), indicating

low-noise performance at practical operational

frequencies. Further, a resistive load inverter based

on GaN-HEMT has been proposed to supplant

existing Silicon-based Complementary Metal Oxide

Semiconductor (CMOS) technology which suffers

from extensive scaling limitations. A thorough

analysis of the inverter circuit has been carried out

through mixed-mode simulation and the effect of the

composition of the barrier layer in the GaN-HEMT, as

well as the supply voltage of the inverter has been

reported. With Si-technology reaching its bottleneck,

GaN based device circuits will surely foster further

research in this domain.

AlN/GaN HEMT with Gate Insulation and Current

Collapse Suppression Using Thermal ALD ZrO2 State Key Laboratory of ASIC and System, School of

Microelectronics, Fudan University, Shanghai, China

College of Electronic and Electrical Engineering, Henan

Normal University ,Xinxiang, China

Journal of Electronic Materials

https://doi.org/10.1007/s11664-019-07524-9

In this letter, we report the device characteristics of AlN/GaN MIS-HEMT on silicon substrate using thermal atomic-layer-deposition (ALD) ZrO2 with various thicknesses. The thermal ALD ZrO2 thin film is deposited at 250°C, which avoids plasma enhancement during the fabrication process. From the transmission electron microscopy results, it is found that the alloy penetrates to the 2DEG region to form a carrier conductive pathway which facilitates the ohmic contact formation. The optimized 7 nm-thick ZrO2 AlN/GaN MIS-HEMT exhibits improved Ion/Ioff ratio and suppressed current collapse degradation, compared with 4 nm-thick ZrO2 AlN/GaN MIS-HEMT and Schottky gate AlN/GaN HEMT (SG-HEMT). In addition, as compared to SG-HEMT, reverse gate leakage current can be reduced by about six orders and forward gate bias extends to + 6.3 V with 7 nm-thick ZrO2 AlN/GaN MIS-HEMT.

https://doi.org/10.1007/s00542-019-04592-z

https://doi.org/10.1007/s11664-019-07524-9


GROUP 5 – MEMS and Sensors Group leader: Marc Faucher (IEMN) Information selected by Knowmade

InGaN microtube optical resonator with sub-

wavelength wall thickness and its application to

refractive index sensing Shaanxi Provincial Key Laboratory of Photonics &

Information Technology and Solid-State Lighting

Engineering Research Center, Xi’an Jiaotong University,

Xi’an 710049, China


https://doi.org/10.1063/1.5098295

Subwavelength freestanding InGaN/GaN quantum

well microtubes with a wall thickness of about 50 nm

are formed by selective release of a coherently

strained bilayer heterostructure from a hosting

substrate. Highly polarized spontaneous and

stimulated emissions due to whispering gallery mode

oscillation were observed in photoluminescence

spectra at room temperature. The quality factor was

increased by a factor of 3 by elevating the microtube

from the substrate and reducing light leakage before

threshold. A lasing threshold was characterized as

low as 3 mJ/cm2. Microtubes were immersed in

different liquids with refractive index variation as

small as 0.01 and tested below and above threshold.

The peak positions shift obviously while exhibiting

excellent repeatability. Using a simple optical probe-

detect method, a 5-μm diameter microtube cavity

achieves a sensitivity of 40 nm/refractive index unit

(RIU) and a detection limit of 6 × 10−3 RIU.

Porous GaN Submicron Rods for Gas Sensor with

High Sensitivity and Excellent Stability at High

Temperature School of Microelectronics, Southern University of

Science and Technology, Shenzhen 518055, China

GaN Device Engineering Technology Research Center of

Guangdong, Southern University of Science and

Technology, Shenzhen 518055, China



Highly porous GaN submicron rods have been

synthesized successfully by a facile hydrothermal

method and heat treatment under controlled

atmosphere. The morphology and size of the

hydrothermal products are tailorable by adjusting the

concentration of precursor solutions. Upon

calcination in air, the nanorod-assembled GaOOH

submicron rods are converted into bundlelike Ga2O3

and into porous GaN submicron rods under an

ammonia flow. Gas-sensing characterization

demonstrates that the sensors based on porous GaN

exhibit high sensitivity and fast response to ethanol

vapor, as well as excellent stability and reliability at

high temperature. The highly porous GaN submicron

rods with a large specific surface area, small grain

size, and high length-to-diameter ratio show better

response to ethanol. A possible sensing enhancement

mechanism is also proposed. This study provides a

promising route for the novel synthesis of GaN

submicron rods for high-performance gas sensors.

Avalanche characteristics in thin GaN avalanche

photodiodes Faculty of Engineering and Technology, Multimedia

University, Jalan Ayer Keroh Lama, 75450 Melaka, Malaysia

Japanese Journal of Applied Physics

https://doi.org/10.7567/1347-4065/ab2e17

A Monte Carlo model using random ionization path

lengths describing the carriers quantum transport in

thin gallium nitride (GaN) avalanche photodiodes

(APDs) for ultraviolet detection in industry is

developed. This work simulated avalanche

characteristics such as impact ionization coefficients,

mean multiplication gain and excess noise factor of

GaN APDs at 0.05 μm, 0.1 μm, 0.2 μm and 0.3 μm

multiplication widths in an electric field. The model

simulates higher electron impact ionization

coefficients than that of the hole for an electric field

greater than 4.04 MV cm−1. Mean multiplication gain

and excess noise factor are simulated based on the

electric field dependent impact ionization

coefficients. Our results show that electron-initiated

multiplication gives higher multiplication gain and

lower excess noise than hole-initiated multiplication

https://doi.org/10.1063/1.5098295


https://doi.org/10.7567/1347-4065/ab2e17


for a multiplication width below 0.3 μm. Devices with

dead space in general give a lower excess noise.

Quality factor improvement of piezoelectric MEMS

resonator by the conjunction of frame structure and

phononic crystals School of Electronic Science and Engineering, University of

Electronic Science and Technology of China, 611731

Chengdu, China

State Key Laboratory of Millimeter Waves and the

Department of Electronic Engineering, City University of

Hong Kong, Hong Kong, China

Institute of Industrial Science, University of Tokyo, Meguro,

153-8505 Tokyo, Japan

Yingcai Honors College, University of Electronic Science

and Technology of China, 611731 Chengdu, China

Sensors and Actuators A: Physical

https://doi.org/10.1016/j.sna.2019.111541

Recently, piezoelectric resonators fabricated by using

MEMS (i.e., micro-electro-mechanical systems)

technology have received increasing attention in a

large and diverse set of applications, including

sensors, filters and timing references. One of the

critical challenges for the actual application of MEMS

resonators is further improving their quality factors

(Qs) to respond the urgent demand of performance

enhancement. Herein, a strategy by employing

suspended frame structure and phononic crystals

(PnC) was proposed to reduce the energy dissipation,

and thus AlN-on-SOI MEMS resonators with high Q

were successfully implemented. The suspended

frame structure isolates the mechanical vibration

between the resonant body and the anchoring

substrate, while PnC arrays serve as a frequency-

selective reflector to reduce the energy leakage. The

multi-physics finite-element-analysis (FEA) and the

experimental comparison were employed to

systematically investigate the underlying mechanisms

of the energy dissipation reduction of the proposed

strategy. The unloaded Qs (i.e., Qu) of proposed

resonators achieved maximum 7.8-fold and 1.5-fold

improvements compared with that of bared

resonators and that of those with only suspended

frame structure, respectively.

pH-Dependent Surface Properties of the Gallium

Nitride – Solution Interface Mapped by Surfactant

Adsorption School of Engineering, The University of Western Australia,

Perth, WA 6009, Australia

School of Molecular Sciences, The University of Western

Australia, Perth, WA 6009, Australia

Material Science and Engineering Department, University

of Washington, Seattle, WA 98195-2120, United States of

America


University of California Santa Barbara, Santa Barbara, CA

93106-9560, United States of America

Journal of Colloid and Interface Science

https://doi.org/10.1016/j.jcis.2019.08.079

The surface charge of gallium nitride (GaN) in contact

with solution is controlled by pH via surface

protonation and deprotonation, similar to silica. Ionic

surfactants adsorb on surfaces via electrostatic and

hydrophobic interactions and can be utilized to

reflect the surface charge of GaN.

Multi-frequency Piezoelectric Micromachined

Ultrasonic Transducers Department of Civil and Materials Engineering,University

of Illinois at Chicago, 842 W Taylor Street ERF 2067,

Chicago IL 60607, U.S.A.

E. L. Ginzton Laboratory, Stanford University, 348 Via

Pueblo, Stanford, CA, 94305, U.S.A.

Skanska, 1436 California Cir, Milpitas, CA, 95035, U.S.A.

IEEE Sensors Journal

https://doi.org/10.1109/JSEN.2019.2935158

In this paper multi-frequency piezoelectric MEMS

ultrasonic transducers (pMUTs) are designed,

characterized and tested for nondestructive

evaluation (NDE) of solids. The transducers operate in

flexural mode, and are tuned to three different

frequencies namely 1 MHz, 1.5 MHz and 2 MHz. The

microstructural layers consist of aluminum nitride

(AlN) as an active sensing layer sandwiched between

metal and doped silicon electrodes. pMUTs are

designed with octagonal and circular membranes.

The vibration of silicon membrane assists

piezoelectric element to convert energies. The

transducers are modeled numerically to obtain their

dynamic characteristics. Piezoelectric Multi-User


https://doi.org/10.1016/j.jcis.2019.08.079



MEMS Processes (PiezoMUMPs) are utilized to

manufacture pMUTs. The electromechanical

characterization shows that the circular design has

higher figure of merit as compared to the octagonal

design due to more uniform stress distribution

transferred between silicon and AlN layers. It is

demonstrated that the piezeoelectric layer should be

deposited up to the inflection point of diaphragm

deformation. This avoids the signal cancellation due

to opposite polarization. The performance of pMUTs

as receiver is evaluated to detect the creep damage

by implementing nonlinear ultrasonic testing (NLUT).

NLUT is based on detecting higher harmonics in solids

due to heterogeneity in materials. Significant

amplification in the second harmonics is obtained

due to highly narrowband and low damping

characteristics of pMUTs that improves the resolution

of NLUT to detect subwavelength damage. Higher

harmonics can be detected using small footprint

pMUT device, which is not possible with conventional

piezoelectric transducers. This allows better spatial

resolution of nonlinear measurement.

Stable Operation of AlGaN/GaN HEMTs for 25 hours

at 400°C in air Department of Aeronautics and Astronautics, Stanford

University, Stanford, CA 94305 USA

Department of Mechanical Engineering, Stanford

University, Stanford, CA 94305 USA

Department of Electrical Engineering and Computer

Science, Massachusetts Institute of Technology (MIT)

Department of Electrical Engineering, Stanford University,

Stanford, CA 94305 USA

IEEE Journal of the Electron Devices Society


Extreme environments such as the Venus

atmosphere are among the emerging applications

that demand electronics that can withstand high-

temperature oxidizing conditions. While wide-

bandgap technologies for integrated electronics have

been developed so far, they either suffer from gate

oxide and threshold voltage (Vth) degradation over

temperature, large power supply requirements, or

intrinsic base current. In this letter, AlGaN/GaN high

electron mobility transistors (HEMTs) are suggested

as an alternative platform for integrated sensors and

analog circuits in extreme environments in oxidizing

air atmosphere over a wide temperature range from

22∘C to 400∘C. An optimal biasing region, with a peak

of transconductance (gm,peak) at –2.3 V with a

negligible shift over the temperature range was

observed. Moreover, remarkably low Vth variation of

0.9% was observed, enabling the design of analog

circuits that can operate over the entire temperature

range. Finally, the operation of the devices at 400∘C

and 500∘C over 25 hours was experimentally studied,

demonstrating the stability of the DC characteristics

after the 5 hours of burn-in, at 400∘C.

3D characterisation of piezoelectric bistable MEMS

membranes during switching Institute of Sensor and Actuator Systems, TU Wien, 1040

Wien, Austria

Sensors and Actuators A: Physical


This paper reports on a novel measurement concept

for the 3D characterisation of bistable MEMS

membranes with an integrated piezoelectric thin film

actuator to stimulate the switching between the two

ground states. Membranes show bistable behaviour

when a characteristic stress value, the so called

critical stress, is exceeded. Sputter-deposited

aluminium nitride (AlN) is used on the one hand as

stress inducing layer and on the other hand to initiate

the switching process. For this purpose, a sequence

of five rectangular voltage pulses with varying peak-

to-peak voltage levels in the range of 30–40 Vpp was

applied. The method to measure the 3D movement

of the membrane during the switching process is

based on a combination of static Whitelight

interferometry (WLI) and dynamic laser Doppler

Vibrometer (LDV) measurements. Thus, an 11 by 11

measurement grid covers the membrane surface

requesting in turn 121 switching processes to

reconstruct the complete membrane trajectory. In

this work two different electrode configurations were

used, namely a fully covered and a four-segmented

cake sliced design. We showed that the switching

modes of the membranes are similar to the

membrane specific eigenmodes, whereas the 01-

mode is preferred by the first and the 11-mode by

the four segmented electrode design. When exciting

only two of the four electrode segments the

switching between the ground states requests a 2.5–




5% lower Vpp but needs seven instead of five pulses.

Assuming that the membrane shape during the

bistable switching process is decisive for some

applications as in e.g. acoustics for sound generation,

this method is most valuable for the characterization

of the basic device performance when exploiting

buckled membranes as key component.

Characterization of an Acetone Detector Based on a

Suspended WO₃-Gate AlGaN/GaN HEMT Integrated

With Microheater Department of Microelectronics, Delft University of

Technology, 2628 CD Delft, The Netherlands

Department of Electrical and Electronic Engineering,

Southern University of Science and Technology, Shenzhen

518055, China

China Research Institute, Delft University of Technology,

100083 Beijing, China

State Key Laboratory of Solid State Lighting, Changzhou

213161, China

USound Shenzhen Office, Shenzhen 518057, China

Shenzhen 3NOD Acousticlink Company, Ltd., Shenzhen

518030, China

Institute of Microelectronic, Tsinghua University, Beijing

10084, China


https://doi.org/10.1109/TED.2019.2936912

A suspended AlGaN/GaN high electron mobility

transistor (HEMT) sensor with a tungsten trioxide

(WO₃) nanofilm modified gate was microfabricated

and characterized for ppm-level acetone gas

detection. The sensor featured a suspended circular

membrane structure and an integrated microheater

to select the optimum working temperature. High

working temperature (300°C) increased the

sensitivity to up to 25.7% and drain current change

IDS to 0.31 mA for 1000-ppm acetone in dry air. The

transient characteristics of the sensor exhibited

stable operation and good repeatability at different

temperatures. For 1000-ppm acetone concentration,

the measured response and recovery times reduced

from 148 and 656 to 48 and 320 s as the temperature

increased from 210 °C to 300 °C. The sensitivity to

1000-ppm acetone gas was significantly greater than

the sensitivity to ethanol, ammonia, and CO gases,

showing low cross-sensitivity. These results

demonstrate a promising step toward the realization

of an acetone sensor based on the suspended

AlGaN/GaN HEMTs.

Development of GaN Transducer and On-Chip

Concentrator for Galvanic Current Sensing Centre for Advanced Low-Carbon Propulsion Systems (C-

ALPS), Institute for Future Transport and Cities, Coventry

University, Coventry CV1 5FB, U.K.

Department of Electrical and Electronics Engineering,

University of Sheffield, Sheffield S37HQ, U.K.

Faculty of Electronic Engineering, University of Nis, 18000

Nis, Serbia


https://doi.org/10.1109/TED.2019.2936687

Gallium nitride (GaN) magnetic high electron mobility

transistors (MagHEMTs) with different gate lengths

intended for integration with magnetic flux

concentrator for galvanic isolation are presented.

Detailed discussions on the physical mechanisms

behind the sensitivity change at room temperature

with respect to gate geometry are given. The relative

sensitivity of dual-drain GaN MagHEMTs with a

device length of L = 65 μm and a width of W = 20 μm

is measured at the highest of S = 17.21%/T and the

lowest of S = 7.69%/T at VGS= -2 V and VGS= 0 V,

respectively. In addition, a novel spiral magnetic flux

concentrator with the conversion factor of up to FC=

96 mT/A is designed for improving the performance

of the optimized MagHEMTs in ICs. It is predicted

that a spiral configuration is a necessity to enhance

the conversion factor for a long MagHEMT.

p-NiO/n-GaN heterostructure diode for temperature

sensor application Institute of Technology and Science, Tokushima University,

Tokushima 770-8506, Japan and Institute of Information

Photonics and Optical Communications, Beijing University

of Posts and Telecommunications (BUPT)

Institute of Technology and Science, Tokushima University,

Tokushima 770-8506, Japan

School of Electronics and Information Technology, Sun Yat-

Sen University, Guangzhou 510275, China

IEEE Sensors Journal


p-NiO/n-GaN heterostructure diodes with different

anode diameters were fabricated and

https://doi.org/10.1109/TED.2019.2936912

https://doi.org/10.1109/TED.2019.2936687



comprehensively characterized for temperature

sensor application. The circular diodes with NiO

anode presented good stability in the temperature

range from 25 to 200 °C. It is found that the

temperature sensitivity is significantly influenced by

the series resistance and ideality factor at the fully-

turn-on state. A sensitivity of 2.58 mV/K was

achieved for the device with a diameter of 100 pm (at

20 mA) and the sensitivity decreased with the

increasing area. In the sub-threshold region, the

forward voltage at a current density also varied

linearly with temperature. The sensitivity shows high

dependence on the forward current density and a

smaller current density is corresponding to a higher

sensitivity.


GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)

Information selected by Knowmade

Effect of Bias on the Response of GaN Axial p–n Junction Single-Nanowire Photodetectors Univ. Grenoble-Alpes, CNRS-Institut Néel, 25 av. des Martyrs, 38000 Grenoble, France Univ. Grenoble-Alpes, CEA-IRIG-PHELIQS, 17 av. des Martyrs, 38000 Grenoble, France Nano Lett. https://doi.org/10.1021/acs.nanolett.9b02040

We present a comprehensive study of the performance of GaN single-nanowire photodetectors containing an axial p–n junction. The electrical contact to the p region of the diode is made by including a p+/n+ tunnel junction as cap structure, which allows the use of the same metal scheme to contact both ends of the nanowire. Single-nanowire devices present the rectifying current–voltage characteristic of a p–n diode but their photovoltaic response to ultraviolet radiation scales sublinearly with the incident optical power. This behavior is attributed to the dominant role of surface states. Nevertheless, when the junction is reverse biased, the role of the surface becomes negligible in comparison to the drift of photogenerated carriers in the depletion region. Therefore, the responsivity increases by about 3 orders of magnitude and the photocurrent scales linearly with the excitation. These reverse-biased nanowires display decay times in the range of ∼10 μs, limited by the resistor-capacitor time constant of the setup. Their ultraviolet/visible contrast of several orders of magnitude is suitable for applications requiring high spectral selectivity. When the junction is forward biased, the device behaves as a GaN photoconductor with an increase of the responsivity at the price of a degradation of the time response. The presence of leakage current in some of the wires can be modeled as a shunt resistance which reacts to the radiation as a photoconductor and can dominate the response of the wire even under reverse bias.

A two-dimensional vertical van der Waals heterostructure based on g-GaN and Mg(OH)2 used as a promising photocatalyst for water splitting: A first-principles calculation School of Mechanical Engineering, Southeast University, Nanjing, Jiangsu 211189, China School of Materials Science and Engineering, Southeast University, Nanjing, Jiangsu 211189, China Journal of Applied Physics https://doi.org/10.1063/1.5099125

In this study, based on first-principles calculation, the structural, electronic, interfacial, and optical properties of two-dimensional (2D) semiconductor vertical heterostructure constructed by g-GaN and Mg(OH)2 are addressed. The g-GaN/Mg(OH)2 heterostructure is discovered to be formed by van der Waals (vdW) forces and possesses a type-II band structure which can promote the separation of photogenerated electron–holes constantly. At the same time, the calculated band edge positions of the heterostructure are decent to induce the oxidation and reduction reactions for water splitting at pH 0. Gibb's free energy change in the redox reaction for the g-GaN/Mg(OH)2 vdW heterostructure is further investigated that the heterostructure can act as a suitable catalyst in hydrogen evolution reaction and oxygen evolution reaction for water splitting. The charge-density difference and the potential drop are calculated across the interface of the g-GaN/Mg(OH)2 vdW heterostructure, and the potential drop can induce a large built-in electric field, which is also a boost to prevent the recombination of the photogenerated charges. Finally, the applied external biaxial strain is studied that it can improve the optical absorption performance of the g-GaN/Mg(OH)2 vdW heterostructure. This study provides a possibility of method to design the 2D vdW heterostructure as a photocatalyst to decompose water.

https://doi.org/10.1021/acs.nanolett.9b02040

https://doi.org/10.1063/1.5099125


Fabrication of an InGaN/GaN nanotube-based photoanode using nano-imprint lithography and a secondary sputtering process for water splitting Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China Institute of Applied Electronics, CAEP, Mianyang 621900, People's Republic of China Research and Development Center for Solid State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100086, People's Republic of China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China Department of Materials Science and Engineering, Korea University, Seoul 137-713, Republic of Korea Department of Electrical and Electronic Engineering, The University of Tokushima, 2-1, Minami-josanjima, Tokushima, 770-8506, Japan Japanese Journal of Applied Physics https://doi.org/10.7567/1347-4065/ab293e

In this research, an InGaN/GaN nanotube-based photoanode has been fabricated by nano-imprint lithography and a secondary sputtering process. The involvement of a Au nano-ring mask allowed dry etching with a high aspect ratio on the InGaN/GaN substrate. After device fabrication, the measured optical spectrum showed this innovative structure provided low reflectance and high absorbance at the wavelength around the ultraviolet range. The photoelectrochemical properties indicated optimized tube height could efficiently enhance the water splitting efficiency by 15 times at 1.23 V versus RHE by increasing the surface reactive area and tuning the optical spectrum properties. The IPCE result also demonstrated a corresponding enhancement.

Nanopyramid-based absorber to boost the efficiency of InGaN solar cells UMI 2958, GT – CNRS, 2 rue Marconi, 57070 Metz, France School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250, USA LIA ATLAS, Université Internationale de Rabat and CNRS, Technopolis Rabat-Shore Rocade Rabat-Salé, 11 100 Sala el Jadida, Morocco Institut Lafayette, 3 rue Marconi 57070 Metz, France Solar Energy https://doi.org/10.1016/j.solener.2019.07.090

InGaN nano-structures, grown using nano selective area growth, have been shown to exhibit high crystalline quality, even for high In content InGaN

alloy, and reduced polarization charge effect. They are thus very attractive for the realization of high efficiency solar cells. Compared to planar InGaN absorbers, nanopyramid-based absorbers are shown to relax the usual challenging constraint on the doping of the p-GaN layer, which would be needed to overcome the polarization-induced electric field. NP-based solar cells maintain the same performance with ten times lower p-GaN doping. Furthermore, the SiO2 mask used for selective area growth of the nanopyramids is shown to help trap light into the nanopyramids, leading to increased optical absorption and thus efficiency. Last, InGaN nanopyramid absorber-based solar cells can allow for a higher InGaN residual donor concentration than that of the planar InGaN solar cells. Overall, an optimized In0.3Ga0.7N nanopyramid-based solar cell can lead to an efficiency twice than that of a planar InGaN-based solar cells with standard p- and n-GaN doping level. As a proof of concept, an In0.09Ga0.91N nanopyramid-based solar cell has been fabricated and is shown to have larger short circuit photocurrent and open circuit voltage than a state of the art In0.08Ga0.92N-based planar solar cell.

Electrocatalytic activity of InN/InGaN quantum dots Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, PR China National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, PR China Academy of Shenzhen Guohua Optoelectronics, Shenzhen 518110, PR China Electrochemistry Communications https://doi.org/10.1016/j.elecom.2019.106514

We present a basic, comprehensive study of the electrocatalytic activity of epitaxial InN/InGaN quantum dots (QDs) by cyclic voltammetry, electrochemical impedance spectroscopy, linear sweep voltammetry and capacitance-voltage measurements, using the ferro/ferricyanide redox probe. Key is the direct proof of the dependence of the catalytic activity on the QD structural properties and of the existence and overall tunability of high positive surface charge on the QDs being in origin of the catalytic activity together with the zero-dimensional electronic properties. This fundamental assessment paves the way to fine-tuning the artificial QD structure as efficient catalyst to further boost the

https://doi.org/10.7567/1347-4065/ab293e

https://doi.org/10.1016/j.solener.2019.07.090

https://doi.org/10.1016/j.elecom.2019.106514


performance of biosensors and photoanodes for solar hydrogen generation.

A Single-Junction Cathodic Approach for Stable Unassisted Solar Water Splitting Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, MI 48109, USA Department of Materials Science and Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109, USA Joule https://doi.org/10.1016/j.joule.2019.07.022

Unassisted solar water splitting is one key step of artificial photosynthesis converting solar energy to chemical fuels. To date, however, there has been no demonstration of efficient and stable semiconductor photoelectrodes without extra surface protection for unassisted solar water splitting. In this work, we show that a single-junction approach of p-type In0.25Ga0.75N nanowires monolithically integrated on n-type Si wafers through an n++/p++-InGaN tunnel junction can drive relatively efficient and stable unassisted water splitting. A photocurrent density of 2.8 mA cm−2 was measured at zero bias versus a platinum counter electrode in a two-electrode configuration, leading to a solar-to-hydrogen efficiency of 3.4%. No performance degradation was observed for ∼300 h of unassisted solar water splitting without using any extra surface protection layers. Such a single-junction photocathode can be further integrated with a narrow band-gap junction, e.g., Si or GaAs, to achieve further improved efficiency for long-term stable solar water splitting.

https://doi.org/10.1016/j.joule.2019.07.022


GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)

NANO

Information selected by Jesús Zúñiga Pérez (CRHEA-CNRS)

Optically invariant InGaN nanowire light-emitting

diodes on flexible substrates under mechanical

manipulation Department of Electrical and Computer Engineering,

University of Waterloo, Waterloo, ON, N2L 3G1, Canada

Waterloo Institute for Nanotechnology, University of

Waterloo, Waterloo, ON, N2L 3G1, Canada


McGill University, Montreal, QC, H3A 0E9, Canada

npj Flexible Electronicsvolume

https://doi.org/10.1038/s41528-019-0059-z

The integration of GaN-based light-emitting diodes

(LEDs) onto flexible platforms provides

opportunities for conformal lighting, wearable

electronics, and bendable displays. While this

technology may enhance the functionality of the

light source, the development of flexible GaN LEDs

suffers from performance degradation, when

mechanical bending is applied during operation. A

unique approach to eliminate the degradation

employs dot-in-wire structures, using cylindrical

light-emitting heterostructures that protrude above

the flexible platform, separating the active light-

emitting region from the bending substrate. Here,

we demonstrate the optical enhancement of

nanowire light emitters by changing the geometric

orientation within a 1 × 1 mm2 array of nanowires

on a flexible platform through bending of the

substrate platform. The flexible structures were

achieved by transferring GaN nanowire LEDs from

sapphire substrates onto flexible polyethylene

terephthalate (PET) using a “paste-and-cut”

integration process. The I–V characteristics of the

nanowire LEDs showed negligible change after

integration onto the PET, with a turn-on voltage of

2.5 V and a forward current of 400 μA at 4 V. A

significant advantage for the nanowire devices on

PET was demonstrated by tilting the LEDs through

substrate bending that increased the

electroluminescence (EL) intensity, while the I–V

characteristics and the EL peak position remained

constant. Through finite-element analysis and

three-dimensional finite-difference time-domain

modeling, it was determined that tilting the

protruding devices changed the effective distance

between the structures, enhancing their

electromagnetic coupling to increase light output

without affecting the electrical properties or peak

emission wavelength of the LEDs.

Mechanisms of inhomogeneous broadening in

InGaN dot-in-wire structures Department of Electrical Engineering and Computer

Science, University of Michigan, 1301 Beal Avenue, Ann

Arbor, Michigan 48109, USA

Department of Physics, University of Michigan, 450

Church St., Ann Arbor, Michigan 48109, USA


https://doi.org/10.1063/1.5111343

Inhomogeneous broadening of semiconductor

nanostructures results from structural and chemical

variations between different nanostructure entities.

Inhomogeneous broadening can have profound

impacts on the optical properties of a

nanostructure array. In this work, various

inhomogeneous broadening mechanisms in

wurtzite InGaN/GaN dot-in-wire (DIW) structures

were investigated, both experimentally and

theoretically. Using lithographically defined

nanostructures, the microscopic variations including

random alloy fluctuations and atomic-scale

thickness fluctuations can be isolated from

macroscopic variations such as size, shape, and

alloy nonuniformity. An epitaxial InGaN/GaN

quantum well sample was patterned into an array

of sparsely spaced dot-in-wire structures and

measured by confocal microphotoluminescence

(PL) at 10 K. Both static (photon energy) and

dynamic (carrier lifetime) properties were

measured. The PL measurement results were

compared to a theoretical model based on the k-

dot-p method under the effective mass

approximation and including the excitonic effect

https://doi.org/10.1038/s41528-019-0059-z

https://doi.org/10.1063/1.5111343


and surface recombinations. Random alloy

fluctuations, atomic-scale thickness fluctuations,

and size variations of the quantum dots were

separately analyzed. It was found that both the

diameter variation and random alloys dominate the

inhomogeneous broadening of photon energies,

while the random alloys dominate the

inhomogeneous broadening of decay rates. The

piezoelectric field in InGaN materials plays a minor

role in increasing the effect of random alloys but

helps suppress the inhomogeneous broadening due

to well-width fluctuations by keeping the electrons

toward the center of the dots.

Absence of Quantum-Confined Stark Effect in GaN

Quantum Disks Embedded in (Al,Ga)N Nanowires

Grown by Molecular Beam Epitaxy Paul-Drude-Institut für Festkörperelektronik, Leibniz-

Institut im ForschungsverbundBerlin e. V.,

Hausvogteiplatz 5–7, 10117 Berlin, Germany

Department of Applied Physics, TU Eindhoven, Den

Dolech 2, 5612 AZ Eindhoven, TheNetherlands

Nano Lett.


Several of the key issues of planar (Al,Ga)N-based

deep-ultraviolet light-emitting diodes could

potentially be overcome by utilizing nanowire

heterostructures, exhibiting high structural

perfection, and improved light extraction. Here, we

study the spontaneous emission of GaN/(Al,Ga)N

nanowire ensembles grown on Si(111) by plasma-

assisted molecular beam epitaxy. The nanowires

contain single GaN quantum disks embedded in

long (Al,Ga)N nanowire segments essential for

efficient light extraction. These quantum disks are

found to exhibit intense light emission at

unexpectedly high energies, namely, significantly

above the GaN bandgap, and almost independent

of the disk thickness. An in-depth investigation of

the actual structure and composition of the

nanowires reveals a spontaneously formed Al

gradient both along and across the nanowire,

resulting in a complex core/shell structure with an

Al-deficient core and an Al-rich shell with

continuously varying Al content along the entire

length of the (Al,Ga)N segment. This compositional

change along the nanowire growth axis induces a

polarization doping of the shell that results in a

degenerate electron gas in the disk, thus screening

the built-in electric fields. The high carrier density

not only results in the unexpectedly high transition

energies but also in radiative lifetimes depending

only weakly on temperature, leading to a

comparatively high internal quantum efficiency of

the GaN quantum disks up to room temperature.

Effect of Bias on the Response of GaN Axial p–n

Junction Single-Nanowire Photodetectors Univ. Grenoble-Alpes, CNRS-Institut Néel, 25 av. des

Martyrs, 38000 Grenoble, France

Univ. Grenoble-Alpes, CEA-IRIG-PHELIQS, 17 av. des

Martyrs, 38000 Grenoble, France

Nano Lett.


We present a comprehensive study of the

performance of GaN single-nanowire

photodetectors containing an axial p–n junction.

The electrical contact to the p region of the diode is

made by including a p+/n+ tunnel junction as cap

structure, which allows the use of the same metal

scheme to contact both ends of the nanowire.

Single-nanowire devices present the rectifying

current–voltage characteristic of a p–n diode but

their photovoltaic response to ultraviolet radiation

scales sublinearly with the incident optical power.

This behavior is attributed to the dominant role of

surface states. Nevertheless, when the junction is

reverse biased, the role of the surface becomes

negligible in comparison to the drift of

photogenerated carriers in the depletion region.

Therefore, the responsivity increases by about 3

orders of magnitude and the photocurrent scales

linearly with the excitation. These reverse-biased

nanowires display decay times in the range of ∼10

μs, limited by the resistor-capacitor time constant

of the setup. Their ultraviolet/visible contrast of

several orders of magnitude is suitable for

applications requiring high spectral selectivity.

When the junction is forward biased, the device

behaves as a GaN photoconductor with an increase

of the responsivity at the price of a degradation of

the time response. The presence of leakage current

in some of the wires can be modeled as a shunt

resistance which reacts to the radiation as a




photoconductor and can dominate the response of

the wire even under reverse bias.

Selective area growth of GaN nanowires on

Si(1 1 1) substrate with Ti masks by molecular

beam epitaxy Department of Electrical and Computer Engineering,

University of Maryland, College Park, MD 20742, US

Journal of Crystal Growth

https://doi.org/10.1016/j.jcrysgro.2019.125181

We present results on the selective area growth

(SAG) of Gallium Nitride (GaN) nanowires on Si

substrate without any buffer layer by radio

frequency plasma-assisted molecular beam epitaxy.

Full selectivity was achieved with a thin Ti metal

film used as a mask. The mask was fabricated with a

lift-off method to avoid damage to the mask or Si

substrate. The growth on the Ti film was totally

suppressed at a low substrate temperature of

840 °C which is by far the lowest critical

temperature for SAG. An InGaN thin layer was

embedded in the GaN nanowires to realize a site

controllable single photon source. Transmission

electron microscopy (TEM) indicates single

crystalline quality of defect-free GaN nanowires and

the embedded InGaN quantum dot structure.

Ordered arrays of defect-free GaN nanocolumns

with very narrow excitonic emission line width ISOM-Dept. Ing. Electrónica, ETSIT, Univ. Politécnica,

28040 Madrid, Spain

Paul-Drude-Institut für Festkörperforschung, Leibniz-

Institut im Forschungsverbund, Hausvogteiplatz 5–7,

10117 Berlin, Germany

Institute of Physics, Otto-von-Guericke University

Magdeburg, Germany



Ordered arrays of very high quality, defect-free GaN

nanocolumns were achieved by selective area

growth following a two step process involving

nanopillar dry etching (top down) and overgrowth

by Molecular Beam Epitaxy (bottom up). A study by

transmission electron microscopy, over more than

50 individual nanocolumns, confirmed the absence

of extended defects, such as dislocations, polarity

inversion domain boundaries and stacking faults.

Low temperature (10 K) photoluminescence

spectrum is dominated by a donor-bound exciton

emission line at 3.472 eV with a line width of

0.5 meV. In addition, a distinct emission line from

the free-exciton A is observed at 3.479 eV. No

traces of emission lines, either at 2.3 eV (Yellow

Band); 3.45 eV (also labeled as UX line and recently

linked to polarity inversion domain boundaries); or

3.42 eV (stacking faults) were observed.

Deep ultraviolet light-emitting diodes based on a

well-ordered AlGaN nanorod array Research and Development Center for Solid State

Lighting, Institute of Semiconductors, Chinese Academy

of Sciences, Beijing 100083, China




Beijing Engineering Research Center for the 3rd

Generation Semiconductor Materials and Application,


State Key Laboratory of Solid-State Lighting, Beijing

100083, China

Photonics Research


The nanorod structure is an alternative scheme to

develop high-efficiency deep ultraviolet light-

emitting diodes (DUV LEDs). In this paper, we first

report the electrically injected 274-nm AlGaN

nanorod array DUV LEDs fabricated by the

nanosphere lithography and dry-etching technique.

Nanorod DUV LED devices with good electrical

properties are successfully realized. Compared to

planar DUV LEDs, nanorod DUV LEDs present >2.5

times improvement in light output power and

external quantum efficiency. The internal quantum

efficiency of nanorod LEDs increases by 1.2 times

due to the transformation of carriers from the

exciton to the free electron–hole, possibly driven by

the interface state effect of the nanorod sidewall

surface. In addition, the nanorod array significantly

facilitates photons escaping from the interior of

LEDs along the vertical direction, contributing to

improved light extraction efficiency. A three-

dimensional finite-different time-domain simulation

is performed to analyze further in detail the TE- and





TM-polarized photon extraction mechanisms of the

nanostructure. Our results demonstrate the

nanorod structure is a good candidate for high-

efficiency DUV emitters.

Consistent description of mesoscopic transport:

Case study of current-dependent

magnetoconductance in single GaN:Ge nanowires Center for Materials Research (LaMa), Justus Liebig

University Giessen, Heinrich-Buff-Ring 16, D-35392

Giessen, Germany

Institute of Experimental Physics I, Justus Liebig

University Giessen, Heinrich-Buff-Ring 16, D-35392

Giessen, Germany

Institute of Solid State Physics, University of Bremen,

Otto-Hahn-Allee 1, D-28359 Bremen, Germany

Institute of Physical Chemistry, Justus Liebig University

Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen,

Germany

PHYSICAL REVIEW B

https://doi.org/10.1103/PhysRevB.100.085409

The so called phase-coherence length lφ and its

relation to the geometrical dimensions of a sample

determine the electronic transport regime.

Different approaches are established for extracting

lφ from magnetotransport data of mesoscopic

systems and need to be cross-checked by using

experimental data on the same model system in

order to ensure an overall consistent theoretical

description. Suitable model systems for testing this

consistency are single GaN:Ge nanowires. Their

magnetoconductance at low temperatures exhibits

universal conductance fluctuations as well as weak

localization effects. We find that the values of lφ

obtained from the established analysis of the

magnitude of the conductance fluctuations rms(ΔG)

decrease with increasing measurement current,

whereas the corresponding values of lφ determined

by the analyses of the correlation field BC and the

weak localization effect yield the same value for lφ

independent of the measurement current used. We

apply and modify the existing theoretical

framework for bias-dependent differential

conductance fluctuations, in order to explain the

decrease of the conductance fluctuations rms(ΔG)

with increasing current density in our dc

measurements. This leads to the same values of lφ

independent of the analysis approach applied to the

same set of data.

Picosecond time-resolved dynamics of energy

transfer between GaN and the various excited

states of Eu3+ ions Department of Physics, Lehigh University, Bethlehem,

Pennsylvania 18015, USA

Department of Physics, West Chester University, West

Chester, Pennsylvania 19383, USA

Division of Materials and Manufacturing Science,

Graduate School of Engineering, Osaka University, 2-1

Yamadaoka, Suita, Osaka 565-0871, Japan

Van der Waals-Zeeman Institute, University of

Amsterdam, Science Park 904, 1098 XH Amsterdam, The

Netherlands

PHYSICAL REVIEW B


To elucidate the energy transfer and reexcitation

processes in Eu-doped GaN layers that are used in

recently developed, highly efficient red light-

emitting diodes, a systematic series of

photoluminescence and time-resolved

photoluminescence (TR-PL) measurements was

performed. Critical insights on how “slow” Eu

processes (∼µs) can compete against fast

semiconductor processes (∼ps) are revealed using

TR-PL with a high temporal resolution, as it is found

that the initial energy transfer from GaN to the

Eu3+ ions takes place rapidly, on a timescale of

<100 ps. Below band-gap resonant excitation was

used to identify the states into which the energy

transfer occurs. For the most efficient Eu defect

complexes, this transfer dominantly occurs directly

into the

5D0 state of Eu3+. Less efficient complexes also

exhibit transfer into the 5D2 state, the emission of

which can be detected using photoluminescence at

low temperature, indicating the importance of the

excitation pathway on device efficiency. Under high

excitation intensity, reexcitation can also occur,

leading to a redistribution of population into the

5D2, 5D1, or 5D0 states.




The characterization of AlGaN nanowires prepared

via chemical vapor deposition School of Physics and Technology, and Center for

Nanoscience and Nanotechnology School of Physics and

Technology, Wuhan University, Wuhan, People’s

Republic of China

Hubei Nuclear Solid Physics Key Laboratory, Hubei,

People’s Republic of China

Journal of Materials Science: Materials in Electronics

https://doi.org/10.1007/s10854-019-01997-4

AlGaN ternary alloys exhibit some superior

properties due to their tunable direct band gap and

make them widely used in the fabrication of

electronic and optoelectronic devices. Here, we

successfully synthesized AlGaN nanowires by

chemical vapor deposition using Al powder, Ga

droplet and ammonia as starting materials with Pd

as catalyst under a moderate growth temperature.

The role of Pd catalyst during the growth has been

systematically studied. We found that not only the

Pd catalyst is the key to the growth of AlGaN

nanowires in large scale, but also the sizes of

catalyst nanoparticles have an important effect on

diameter distribution of nanowires. XRD and

HRTEM measurements confirmed that the

synthesized AlGaN nanowires are the wurtzite

structure and grown along [001] direction. The

growth time and ammonia flow have important

influence on the morphology of the AlGaN

nanostructures. Based on the evolution of the

nanostructures, we verified that the growth of the

AlGaN nanostructures are affected by both VLS and

VS mechanism and explained the growth process.

NON POLAR / SEMI POLAR Information selected by

Philippe de Mierry Elimination of Stacking Faults in Semipolar GaN

and Light-Emitting Diodes Grown on Sapphire Department of Electrical Engineering, Yale University,

New Haven, CT 06520, USA

Saphlux Inc, Branford, CT 06405, USA

Department of Mechanical Engineering & Materials

Science, Yale University, New Haven, CT 06520, USA



We report a novel approach to eliminate stacking

faults (SFs) and prepare large-area, SF-free

semipolar gallium nitride (GaN) on sapphire

substrates. A root cause of the formation of basal-

plane SFs is the emergence of N-polar (0001̅) facets

during semipolar and nonpolar heteroepitaxies.

Invoking the concept of kinetic Wulff plot, we

succeeded in suppressing the occurrence of N-polar

GaN (0001̅) facets and, consequently, in eliminating

the stacking faults generated in (0001̅) basal planes.

Furthermore, InGaN light-emitting diodes with

promising characteristics have been produced on

the SF-free semipolar (2021̅) GaN on sapphire

substrates. Our work opens up a new insight into

the heteroepitaxial growth of nonpolar/semipolar

GaN and provides an approach of producing SF-free

nonpolar/semipolar GaN material over large-area

wafers, which will create new opportunities in GaN

optoelectronic and microelectronic research.

Demonstration of blue semipolar (2021̲̲) GaN-

based vertical-cavity surface-emitting lasers Materials Department, University of California, Santa




Optics Express

https://doi.org/10.1364/OE.27.023707

We successfully demonstrated an electrically

injected blue (2021̲̲) semipolar vertical-cavity

surface-emitting laser with a 5λ cavity length, an ion

implanted aperture, and a dual dielectric DBR

design. The peak power under pulsed operation

https://doi.org/10.1007/s10854-019-01997-4


https://doi.org/10.1364/OE.27.023707


was 1.85 mW, the threshold current was 4.6

kA/cm2, and the differential efficiency was 2.4% for

the mode at 445 nm of a device with a 12 µm

aperture. Lasing was achieved up to a 50% duty

cycle and the thermal impedance was estimated to

be 1800 K/W. The lasing emission was found to be

100% plane polarized along the a-direction.

Realization of thin-film m-plane InGaN laser diode

fabricated by epitaxial lateral overgrowth and

mechanical separation from a reusable growth

substrate Materials Department, University of California, Santa

Barbara, California 93106, USA


University of California, Santa Barbara, California 93106,

USA

Department of Engineering and Architecture, University

of Trieste, via A.Valerio 10, 34127 Trieste, Italy

Optics Express

https://doi.org/10.1364/OE.27.024717

A nonpolar edge emitting thin film InGaN laser

diode has been separated from its native substrate

by mechanical tearing with adhesive tape,

combining the benefits of Epitaxial Lateral

Overgrowth (ELO) and cleavability of nonpolar GaN

crystal. The essence of ELO is mainly to weakening

strength between native substrate and the

fabricated laser device on top of it. We report a 3

mm long laser bar removed from its native GaN

substrate. We confirmed edge emitting lasing

operation after cleaving facets on a separated thin

bar. Threshold current density of the laser was

measured to be as low as 2.15 kA/cm2.

Effect of high-temperature AlN buffer on

anisotropy of semi-polar (11-22) GaN with two

pressure growth stages Key Laboratory of Opto-electronics Technology, Ministry

of Education, College of Microelectronics, Beijing

University of Technology, People's Republic of China

Micro & Nano Letters

https://doi.org/10.1049/mnl.2018.5669

The low-temperature GaN (LT-GaN) and high-

temperature AlN (HT-AlN) buffer layers were grown

on m -plane sapphire by metal-organic chemical

vapour deposition. The following semi-polar (11-22)

GaN thin films were deposited under high- and low-

pressure growth stages. Anisotropy of (11-22) GaN

grown on HT-AlN buffer along two in-planar

directions ([11-2-3] and [-1100]) were clearly

suppressed, the maximum variation of the X-ray

rocking curve full width at half maximum of (11-22)

GaN on LT-GaN buffer was 0.2498°, that of (11-22)

GaN on HT-AlN buffer was 0.0488°. The X-ray

diffraction results of on-axis and off-axis both

indicated that the crystal quality of the epitaxial

GaN layer with HT-AlN buffer was obviously

improved, and surface morphology was much

smoother.

Improvement in the crystal quality of non-polar a-

plane GaN directly grown on an SiO2 stripe-

patterned r-plane sapphire substrate Key Laboratory for Renewable Energy, Beijing Key

Laboratory for New Energy Materials and Devices, Beijing

National Laboratory for Condensed Matter Physics,

Institute of Physics, Chinese Academy of Sciences, Beijing

100190, China

Center of Materials and Optoelectronics Engineering,

University of Chinese Academy of Sciences, Beijing

100049, China

Songshan Lake Materials Laboratory, Dongguan,

Guangdong 523808, China

CrystEngComm

https://doi.org/10.1039/C9CE00995G

We studied the non-polar a-plane GaN directly

grown on an SiO2 stripe-patterned r-plane sapphire

substrate along the [0001] crystallographic

direction of GaN. The XRC-FWHM values of the

optimized a-plane GaN were 386 arcsec along the c-

axis and 289 arcsec along the m-axis. Detailed

scanning electron microscopy (SEM), X-ray

diffraction (XRD) reciprocal space maps (RSMs) and

Raman scattering studies were performed to

investigate the growth kinetics. It was found that

the increase in mosaic block dimension could be the

primary reason for the improved crystal quality.

This work shows a very promising and simple

method to achieve high-quality a-plane GaN films.

https://doi.org/10.1364/OE.27.024717

https://doi.org/10.1049/mnl.2018.5669

https://doi.org/10.1039/C9CE00995G


Study of efficient semipolar (11-22) InGaN green

micro-light-emitting diodes on high-quality (11-22)

GaN/sapphire template Materials Department, University of California, Santa


Institute of Nano Optoelectronics Research and

Technology, Universiti Sains Malaysia, 11800 USM,

Penang, Malaysia



CNRS-CRHEA, Rue Bernard Gregory, 06560 Valbonne,

France

Optics Express

https://doi.org/10.1364/OE.27.024154

We investigated the electrical and optical

performances of semipolar (11-22) InGaN green

µLEDs with a size ranging from 20 × 20 µm2 to 100

× 100 µm2, grown on a low defect density and large

area (11-22) GaN template on patterned sapphire

substrate. Atom probe tomography (APT) gave

insights on quantum wells (QWs) thickness and

indium composition and indicated that no indium

clusters were observed in the QWs. The µLEDs

showed a small wavelength blueshift of 5 nm, as

the current density increased from 5 to 90 A/cm2

and exhibited a size-independent EQE of 2% by

sidewall passivation using atomic-layer deposition,

followed by an extremely low leakage current of

~0.1 nA at −5 V. Moreover, optical polarization

behavior with a polarization ratio of 40% was

observed. This work demonstrated long-wavelength

µLEDs fabricated on semipolar GaN grown on

foreign substrate, which are applicable for a variety

of display applications at a low cost.

MATERIAL / CHARACTERIZATION / EQUIPMENT / NUMERICAL SIMULATION

Information selected by Agnès Trassoudaine (Université d'Auvergne), Yvon

Cordier and Mathieu Leroux (CRHEA-CNRS)

Defect-rich GaN interlayer facilitating the

annihilation of threading dislocations in polar GaN

crystals grown on (0001)-oriented sapphire

substrates Institute of Materials Science, TU Bergakademie Freiberg,

Gustav-Zeuner-Str. 5, D-09596 Freiberg, Germany

Institute of Nonferrous Metallurgy and Purest Materials,

TU Bergakademie Freiberg, Leipziger Str. 34, D-09596

Freiberg, Germany

Institute of Theoretical Physics, TU Bergakademie

Freiberg, Leipziger Str. 23, D-09596 Freiberg, Germany

Institute of Materials Research, Helmholtz-Zentrum

Geesthacht, Notkestr. 85, D-22607 Hamburg, Germany

Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, D-

22607 Hamburg, Germany

National Research Tomsk Polytechnic University (TPU),

Lenin Avenue 30, 634050 Tomsk, Russian Federation


https://doi.org/10.1063/1.5092284

The interaction of microstructure defects is

regarded as a possible tool for the reduction of the

defect density and improvement of the crystal

quality. In this study, this general approach is

applied to reduce the density of threading

dislocations in GaN crystals grown using high-

temperature vapor phase epitaxy directly on

(0001)-oriented sapphire substrates. The GaN

crystals under study were deposited in three steps

with different process temperatures, growth rates,

and ammonia flows. The first GaN layer

accommodates the lattice misfit between sapphire

and gallium nitride. Thus, it contains a high number

of randomly distributed threading dislocations. The

next GaN layer, which is internally structured and

defect-rich, bends and bunches these dislocations

and facilitates their annihilation. The uppermost

GaN layer mainly contains bunched threading

dislocations terminating large areas of almost

defect-free GaN. In order to be able to visualize and

to quantify the microstructure changes in individual

parts of the sandwich-like structure, the samples

were investigated using nanofocused synchrotron

https://doi.org/10.1364/OE.27.024154

https://doi.org/10.1063/1.5092284


diffraction, confocal micro-Raman spectroscopy,

and transmission electron microscopy. The

transmission electron microscopy provided

information about the kind of microstructure

defects and their mutual interaction. The

synchrotron diffraction and the micro-Raman

spectroscopy revealed the depth profiles of

dislocation density and lattice parameters.

The role of Mg bulk hyper-doping and delta-doping

in low-resistance GaN homojunction tunnel diodes

with negative differential resistance Georgia Institute of Technology, Atlanta, Georgia 30332,

USA

Arizona State University, Tempe, Arizona 85281, USA

Photonitride Inc., Tempe, Arizona 85284, USA


https://doi.org/10.1063/1.5112498

GaN p++/n++ tunnel junctions (TJs) with heavy bulk

or delta Mg doping at the junction were grown via

molecular beam epitaxy with a hysteresis-free and

repeatable negative differential resistance (NDR).

The TJ with Mg doping of 5.5 × 1020 cm−3 shows

NDR at ∼1.8 V and a large current density of

3.4 KA/cm2 at −1.0 V. Atomic resolution scanning

transmission electron microscopy imaging showed

no additional defects despite the doping exceeding

the solubility limit in GaN allowing subsequent

epitaxy of series-connected layers and devices. GaN

homojunction TJs grown on bulk GaN showed an

improved current density and NDR stability. In

addition, the effect of Mg delta doping at the

junction was investigated for the first time showing

a dramatic improvement in the tunneling

characteristics. A metal-organic chemical vapor

deposition (MOCVD) grown InGaN light-emitting

diode (LED) with an MBE grown GaN homojunction

tunnel contact to the MOCVD grown p-GaN layer

shows superior lateral conductivity and improved

luminescence uniformity, but suffers an added

voltage penalty, assumed to be due to interface

impurities, compared to control LED with indium-

tin-oxide.

Absorption in ultrathin GaN-based membranes:

The role of standing wave effects Department of Materials Science and Technology,

University of Crete, P.O. Box 2208, 71003 Heraklion,

Greece

Microelectronics Research Group, IESL-FORTH, P.O. Box

1385, 71110 Heraklion, Greece

Université Grenoble-Alpes, CEA, INAC-PHELIQS, 17 av.

des Martyrs, 38000 Grenoble, France


https://doi.org/10.1063/1.5112173

A methodology is described to extract the

absorption coefficient spectrum and exciton

oscillator strength of GaN layers and GaN/AlGaN

quantum wells by analyzing microtransmittance

experiments in high-quality, free-standing

membranes with thicknesses in the 160–230 nm

range. The absorbance of a subwavelength GaN

membrane is found to be an oscillating function of

its thickness, in keeping with the standing wave

effect. We analyze our results using two alternative

models including interference effects and extract

identical absorption coefficient values. The room-

temperature absorption coefficient of bulk GaN

membranes at the main exciton peak is found to be

9 × 104 cm−1. In the case of GaN/AlGaN quantum

wells, the enhancement and blue shift of the

excitonic absorption are observed, as a result of

quantum confinement.

Extra half-plane shortening of dislocations as an

origin of tensile strain in Si-doped (Al)GaN Ferdinand-Braun-Institut, Leibniz-Institut für

Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489

Berlin, Germany

Institute of Physics, Humboldt University of Berlin,

Newtonstr.15, 12489 Berlin, Germany


https://doi.org/10.1063/1.5111664

Si doping of (Al,Ga)N layers grown by metalorganic

chemical vapor deposition induces an inclination of

threading dislocations (TDs). This inclination leads

to a change of the extra half-plane size of edge and

mixed type dislocations. Depending on the

dislocation density and the doping concentration,

these effects are accompanied by the generation of

https://doi.org/10.1063/1.5112498

https://doi.org/10.1063/1.5112173

https://doi.org/10.1063/1.5111664


tensile strain, which can also lead to crack

formation. Several models have been published in

the past in order to explain this process. Different

models result in opposite TD inclination directions

with respect to the extra half-plane position.

Therefore, this work examines the correlation

between the extra half-plane position and the

inclination direction to clarify the origin of the

tensile strain increase using scanning transmission

electron microscopy. With this approach, it can be

unambiguously experimentally verified that Si

doping leads to a shortening of the dislocations

half-plane. An analysis of in situ wafer curvature

measurement proves that the increase of tensile

strain in GaN caused by Si doping can be explained

by this process. Aside from the inclination caused

by Si doping, a TD inclination in undoped GaN layers

has been analyzed. Possible explanations for the

inclination process are discussed.

Study of electronic transport properties in

AlGaN/AlN/GaN/AlGaN double-heterojunction

transistor Department of Electronic Engineering, Xi’an University of

Technology, Xi’an 710048, China

State Key Discipline Laboratory of Wide Bandgap

Semiconductor Technologies, School of Microelectronics,

Xidian University, Xi’an 710071, People's Republic of

China


https://doi.org/10.1063/1.5116042

The electronic transport properties in

AlGaN/AlN/GaN/AlGaN double heterostructures are

investigated by an analytical model, considering the

effect of the modified Fang-Howard wave function.

The alloy disorder scattering is assumed to be

eliminated by the introduction of an AlN insertion

layer, and the rest five possible scattering

mechanisms, acoustic deformation potential

scattering, piezoelectric field scattering, polar

optical phonons scattering, interface roughness

scattering, and dislocation scattering, are taken into

consideration in the calculation. The relations of

two-dimensional electron gas (2DEG) density and

mobility with alloy composition in the top AlGaN

barrier layer and AlGaN buffer layer and the

channel thickness are estimated and discussed.

Finally, we compare the temperature dependences

of the 2DEG mobility in

Al0.25Ga0.75N/AlN/GaN/Al0.05Ga0.95N double

heterostructures and in the conventional

Al0.25Ga0.75N/AlN/GaN single heterostructures

and explain them with detailed scattering

processes.

Heteroepitaxial growth of GaN on sapphire

substrates by high temperature vapor phase

epitaxy Fraunhofer Institute for Integrated Systems and Device

Technology IISB, Schottkystraße 10, 91058 Erlangen,

Germany

Institute of Nonferrous Metallurgy and Purest Materials,

TU Bergakademie Freiberg, Leipziger Straße 34, 09599

Freiberg, Germany

Institute of Materials Science, TU Bergakademie Freiberg,

Gustav-Zeuner-Straße 5, 09599 Freiberg, Germany

Institute of Theoretical Physics, TU Bergakademie

Freiberg, Leipziger Straße 23, 09599 Freiberg, Germany

Institute of Applied Physics, TU Bergakademie Freiberg,

Leipziger Straße 23, 09599 Freiberg, Germany



This paper presents recent progress in the

development of the high temperature vapor phase

epitaxy (HTVPE) for a direct deposition of GaN

layers on sapphire substrates and the impact of the

improved deposition technique on the quality of

the HTVPE GaN layers. This technique uses an

improved HTVPE reactor for a better control of the

growth process. The reactor contains a newly

designed Ga evaporation cell made of refractory

metals, which significantly reduces the

concentration of process-induced impurities. As a

result, the impurity concentrations in the HTVPE

layers were reduced to or below 1016 cm−3. For a

direct deposition of GaN on (0001)-oriented

sapphire, a multi-step process was developed that

includes the growth of a nucleation layer and a seed

layer, which can be used as a template for further

overgrowth with an increased growth rate to

produce several ten µm thick GaN layers. The

properties of the HTVPE layers are characterized by

optical and scanning electron microscopy, glow

discharge mass spectrometry, Raman spectroscopy,

https://doi.org/10.1063/1.5116042



X-ray diffraction, and photoluminescence. The

residual stresses and dislocation densities are

presented for seed and overgrown layers, and

compared with the properties of layers grown by

established methods of chemical vapor phase

epitaxy. In this context, challenges and prospects of

the HTVPE method are discussed.

Investigation of MOVPE-grown zincblende GaN

nucleation layers on 3C-SiC/Si substrates Department of Materials Science and Metallurgy,

University of Cambridge, 27 Charles Babbage Road,

Cambridge CB3 0FS, United Kingdom

Institute of Physics of Materials & CEITEC IPM, Academy

of Sciences of the Czech Republic, Žižkova 22, 61600

Brno, Czech Republic

Centre for High Frequency Engineering, University of

Cardiff, 5 The Parade, Newport Road, Cardiff CF24 3AA,

United Kingdom



Cubic zincblende (zb-)GaN nucleation layers (NLs)

grown by MOVPE on 3C-SiC/Si substrates were

studied to determine their optimal thickness for

subsequent zb-GaN epilayer growth. The layers

were characterised by atomic force microscopy, X-

ray diffraction and scanning transmission electron

microscopy. The as-grown NLs, with nominal

thicknesses varying from 3 nm to 44 nm, consist of

small grains which are elongated in the [1 −1 0]

direction, and cover the underlying SiC surface

almost entirely. Thermal annealing of the NLs by

heating in a H2/NH3 atmosphere to the elevated

epilayer growth temperature reduces the substrate

coverage of the films that are less than 22 nm thick,

due to both material desorption and the ripening of

islands. The compressive biaxial in-plane strain of

the NLs reduces with increasing NL thickness to the

value of relaxed GaN for a thickness of 44 nm. Both

the as-grown and annealed NLs are crystalline and

have high zincblende phase purity, but contain

defects including misfit dislocations and stacking

faults. The zb-GaN epilayers grown on the thinnest

NLs show an enhanced fraction of the wurtzite

phase, most likely formed by nucleation on the

exposed substrate surface at elevated temperature,

thus dictating the minimum NL thickness for phase-

pure zb-GaN epilayer growth.

Effect of a SiC seed layer grown at different

temperatures on SiC film deposition on top of an

AlN/Si(110) substrate Graduate School of Science and Technology, Hirosaki

University, 3 Bunkyo, Hirosaki, Aomori 036-8561, Japan


https://doi.org/10.7567/1347-4065/ab23fa

We have formed silicon carbide (SiC) seed layers at

various substrate temperatures by ultralow-

pressure chemical vapor deposition using

monomethylsilane (CH3SiH3) on aluminum nitride

(AlN) films grown on off-axis Si(110) substrates.

After that, we grew SiC films on the seed layers by

pulsed laser deposition using a SiC target. We

investigated the effects of the seed layers formed at

various temperatures on the crystallinity and

surface morphology of the SiC films thereon. The

SiC films grown on the seed layers tended to have

lower surface roughnesses than the film grown

directly on the AlN film. The SiC film grown on the

seed layer formed at 600 °C on the AlN film had the

best crystallinity among the films. The formation of

the seed layers had an effect on the relaxation of

the internal stress in the SiC films. The SiC film can

be used to grow epitaxial graphene by high-

temperature annealing, and the AlN layer on Si

plays a role in insulating graphene devices from the

Si substrate. Therefore, the graphene transistors

are one of the possible applications for epitaxial

graphene grown on SiC/AlN/Si.

Growth of 3C-SiC(111) on AlN/off-axis Si(110)

hetero-structure and formation of epitaxial

graphene thereon Graduate School of Science and Technology, Hirosaki

University, 3 Bunkyo, Hirosaki, Aomori 036-8561, Japan


https://doi.org/10.7567/1347-4065/ab2536

A cubic silicon carbide (3C-SiC) film was fabricated

by pulsed laser deposition on an aluminum nitride

layer grown on an off-axis Si(110) substrate. This is

the first report about the use of off-axis Si(110)


https://doi.org/10.7567/1347-4065/ab23fa

https://doi.org/10.7567/1347-4065/ab2536


substrates for manufacturing SiC/AlN/Si multilayers.

A high-quality epitaxial 3C-SiC(111) film without

rotation domains or twins, as evidenced by

reflection high-energy electron diffraction (RHEED)

measurements, was successfully obtained by using

a wurtzite AlN(0001)/off-axis Si(110) substrate. On

this 3C-SiC film, graphene was formed through

annealing in ultrahigh vacuum at 1200 °C and its

structure and chemical bonding were investigated

via in situ RHEED and X-ray photoelectron

spectroscopy; the full width at half maximum of the

C 1s core level peak and the root-mean-square

surface roughness were 0.60 eV and 0.14 nm,

respectively, which were substantially lower than

those (0.73 eV and 1.44 nm) previously reported for

a graphene sample with similar thickness but

formed on a SiC/AlN/on-axis Si(110) substrate.

Impact of the substrate lattice constant on the

emission properties of InGaN/GaN short-period

superlattices grown by plasma assisted MBE Institute of High Pressure Physics, Polish Academy of

Sciences, Sokołowska 29/37, 01-142 Warszawa, Poland

Paul Drude Institut für Festkörperelektronik,

Hausvogteiplatz 5-7, 10117 Berlin, Germany

TopGaN Ltd, Sokołowska 29/37, 01-142 Warszawa,

Poland

Leibniz-Institute for Crystal Growth, Max-Born-Str. 2,

12489 Berlin, Germany



In this work we investigate InGaN/GaN short period

superlattices (SPSLs) grown on (0001) GaN and on

relaxed In0.2Ga0.8N buffers with varying degree of

plastic relaxation. The SPSLs were fabricated by

plasma assisted molecular beam epitaxy (PAMBE).

Despite the nominal SPSL structure consisted of InN

monolayers (MLs) embedded in GaN barriers, we

observed single monolayer InGaN layers instead of

InN. We study the photoluminescence (PL) of such

SPSLs as a function of the substrates lattice

constant. Increase of the substrate lattice constant

from a = 3.183 Å (for GaN grown on sapphire) to

a = 3.216 Å resulted in a peak emission shift from

379 nm to 419 nm. We attribute the PL red-shift to

the increased In incorporation in the ML-thick

InGaN on relaxed buffers as a consequence of the

reduced lattice mismatch between the substrate

and the film. Our experiment confirms that

coherent growth of InN is prohibited on GaN and

points out the important role of substrate lattice

constant engineering for realization of InN/GaN

SPSLs.

Electronic properties of air-exposed GaN(11-00)

and (0001) surfaces after several device processing

compatible cleaning steps Paul-Drude-Institut für Festkörperelektronik, Leibniz-

Institut im Forschungsverbund Berlin e.V.,

Hausvogteiplatz 5–7, Berlin 10117, Germany

InnovationLab, Speyerer Str. 4, Heidelberg 69115,

Germany

Materials Science Department, Technische Universität

Darmstadt, Otto-Berndt-Strasse 3, Darmstadt 64287,

Germany

Institute for High-Frequency Technology, Technische

Universität Braunschweig, Germany

Kirchhoff Institute for Physics, Heidelberg University, Im

Neuenheimer Feld 227, Heidelberg 69120, Germany

Grupo de Electrónica y Semiconductores, Dpto. Física

Aplicada, Universidad Autónoma de Madrid, C/ Francisco

Tomás y Valiente 7, Madrid 28049, Spain

Applied Surface Science

https://doi.org/10.1016/j.apsusc.2019.07.256

We report on the electronic properties of GaN and

(0001) surfaces after three different and

subsequent device processing compatible cleaning

steps: HCl etching, annealing at 400 °C in N2

atmosphere, and O2 plasma exposure. The surface

electronic properties are quantified, in the dark and

under ultraviolet illumination, using X-ray

photoelectron spectroscopy and a Kelvin probe. We

find that the cleaning steps largely affect the work

function and the band bending of both GaN

orientations. These modifications are attributed to

the presence of different surface states as well as to

the formation of adsorbates building up distinct

surface dipoles. Besides these results, we detect

that under ultraviolet illumination the work

function of the surfaces exposed to HCl decreases

by at least 0.2 eV without screening of the band

bending. We thus attribute the observed surface

photovoltage to a photo-induced modification of

the surface dipole. Overall, these results emphasize

the strong dependence of the electronic properties


https://doi.org/10.1016/j.apsusc.2019.07.256


of air-exposed GaN surfaces on adsorbates. As a

result, we advocate the use of the common

cleaning steps analyzed here to re-initialize at will

GaN and (0001) surfaces into pre-defined states.

Comparative study of AlGaN/GaN heterostructures

grown on different sapphire substrates Wide Bandgap Semiconductor Technology Disciplines

State Key Laboratory, School of Microelectronics, Xidian

University, Xi'an, 710071, China



AlGaN/GaN heterostructures were grown on the

conventional planar sapphire substrate (CSS), nano-

scale patterned sapphire substrate (NPSS) and

micro-scale patterned sapphire substrates (MPSS)

by metal organic chemical vapor deposition

respectively. The heterostructure grown on the

MPSS has significantly lower threading dislocation

density (TDD) than those grown on the NPSS and

CSS. The bending and quenching of threading

dislocations induced by lateral growth are the main

factors for the reduction of TDD. Correspondingly,

the carrier mobility of heterostructure grown on the

MPSS is also the highest.

Electrochemical Modeling of the Effects of F Ions in

the AlGaN Layer on the Two-Dimensional Electron

Density in AlGaN/GaN HEMTs School of Computer & Communication Engineering,

University of Science & Technology Beijing, Haidian

District Beijing 100083, China


https://doi.org/10.1149/2.0111909jss

Based on electrochemical principles, a new physical

model of the F ions in the AlGaN layer on the two-

dimensional electron gas of GaN transistors is

proposed. The two-dimensional electron gas

affected by the F ions in the AlGaN layer calculated

by the proposed model can explain those

experimental observations reported in the

literature. According to the proposed model, the

two-dimensional electron gas could physically

origins from the electromotive force in the solid

electrolyte-the AlGaN layer. The proposed model

predicates howthe width of the compact layer, the

temperature, the degree of ionization and F ions in

the AlGaN layer impacts on the two-dimensional

electron gas that still remains to be unraveled. The

proposed modelgives a physical understanding

ofhow F ions impacts on the performance of GaN-

based transistors and supplies a possibility to

improve their performance.

Three-dimensional band diagram in lateral polarity

junction III-nitride heterostructures Ningbo Institute of Materials Technology and

Engineering, Chinese Academy of Sciences, Ningbo

315201, Zhejiang, China

Advanced Semiconductor Laboratory, King Abdullah

University of Science and Technology (KAUST), Thuwal

23955, Saudi Arabia

Physical Science and Engineering Division, King Abdullah

University of Science and Technology (KAUST), Thuwal

23955, Saudi Arabia

University of Chinese Academy of Sciences, Beijing

100049, China

ShanghaiTech University, Pudong, Shanghai 201210,

China

Hebei University of Technology, Institute of Micro-Nano

Photoelectron and Electromagnetic Technology

Innovation, School of Electronics and Information

Engineering, Tianjin 300401, China

School of Molecular Sciences, University of Western

Australia, Perth 6009, Australia

Optica

https://doi.org/10.1364/OPTICA.6.001058

The 2D band diagram comprising out-of-plane

potentials has been ubiquitously utilized for III-

nitride heterostructures. Here, we propose the 3D

band diagram based on unambiguous evidences in

luminescence and carrier dynamics for lateral

polarity junction quantum wells: although electrons

and holes are separated out-of-plane in quantum

wells by polarization, different band diagram

heights lead to secondary carrier injection in-plane,

causing electrons to transport from the III- to N-

polar domains to recombine with holes therein with

large wavefunction overlap. We also show that

utilization of the 3D band diagram can be extended

to single-polarity structures to analyze carrier

transport and dynamics, providing new dimensions

for accurate optical device design.


https://doi.org/10.1149/2.0111909jss

https://doi.org/10.1364/OPTICA.6.001058


On the determination of alloy composition using

optical spectroscopy in MOVPE grown InGaN

layers on Si(111) Solid State Physics Laboratory, Defence R&D

Organisation, Timarpur, Delhi, 110054, India

Centre for Nano Science and Engineering, Indian Institute

of Science, Bangalore, 560012, India

Semiconductor Materials Lab., Materials Science Section,

Raja Ramanna Centre for Advanced Technology, Indore,

M.P, 452013, India

Dept. of Condensed Matter Physics and Material Science,

Tata Institute of Fundamental Research, Homi Bhabha

Road, Mumbai, 400005, India

Homi Bhabha National Institute, Training School

Complex, Anushakti Nagar, Mumbai, 400094, India



Alloy composition of InxGa1-xN layer is investigated

using photoluminescence (PL), and

photoluminescence excitation (PLE) techniques.

InGaN layers were grown on Si(111) substrates

using metal organic vapour phase epitaxy (MOVPE)

technique under variable flow of either ammonia

(NH3) or trimethyl gallium (TMGa) with

corresponding V/III ratios in the range of 3.6 × 103

to 1.2 × 104. We observed that though room

temperature PL measurements give an indication

about the growth of InGaN, it doesn't help in the

estimation of band gap or alloy composition of

layer. It is restricted mainly by the presence of

multiple peaks in the PL spectra which is rather

severe at low temperature. A comparison of PL and

reflectivity spectra confirmed that such peaks are

attributed to interference oscillations and are not

related with multiple compositions of InGaN.

Further, in such a scenario PLE is found to be quite

effective where the measured PLE spectrum is

consisted of a clear onset related to InGaN layer in

the sub band gap region of GaN. It is quite helpful in

a precise determination of band gap and hence the

alloy composition of InGaN layer. The indium

composition is estimated to be in the range of

3.5% ≤ x ≤ 20.5%, however its trends with respect to

V/III ratio as a function of NH3 or TMGa flow are

found to be rather opposite.

Infrared reflectance characterization of porous

GaN thin films on sapphire substrate using

factorized-Rayleigh model School of Physics, Universiti Sains Malaysia, 11800,

Minden, Penang, Malaysia

Institute of Nano-Optoelectronics Research and

Technology (INOR), Universiti Sains Malaysia, Bukit

Jambul, 11900, Bayan Lepas, Penang, Malaysia

Optical Materials

https://doi.org/10.1016/j.optmat.2019.109320

The surface morphology dependence of porous

gallium nitride (PGaN) thin film on infrared (IR)

dielectric response was investigated using s-

polarized IR reflectance technique. Porosity-

induced resonances, namely, Fröhlich modes, were

observed in the reststrahlen region of PGaN.

Several phenomenological effective medium

theories (EMTs), i.e., Maxwell Garnett, Bruggeman,

Looyenga, Lichtenecker, and Rayleigh (Ra) models,

were used to simulate the dielectric function and

Fröhlich modes of PGaN. Among the EMTs, only the

Ra model successfully predicts all resonant features

that originated from Fröhlich modes. Finally, the Ra

model is reformulated in factorized form to take

into account the damping of Fröhlich modes and

Fröhlich-plasmon coupling. Given the good fitness

of experimental and simulated spectra and with the

reasonable prediction of Fröhlich modes,

factorized-Ra model is determined to be the most

appropriate EMT to describe the IR dielectric

response of PGaN with cylindrical air hole.

Improvement of TE-polarized emission in type-II

InAlN–AlGaN/AlGaN quantum well School of Information Science and Technology & Tongke

School of Microelectronics, Nantong University, Nantong

226019, China

Chinese Physics B

https://doi.org/10.1088/1674-1056/ab343a

The optical properties of the type-II lineup In x

Al1−x N–Al0.59Ga0.41N/Al0.74Ga0.26N quantum

well (QW) structures with different In contents are

investigated by using the six-by-six K–P method. The

type-II lineup structures exhibit the larger product

of Fermi–Dirac distribution functions of electron


https://doi.org/10.1016/j.optmat.2019.109320

https://doi.org/10.1088/1674-1056/ab343a


fn,c and hole (1-fv,Um) and the approximately

equal transverse electric (TE) polarization optical

matrix elements |Mx|2 for the c1–v1 transition. As a

result, the peak intensity in the TE polarization

spontaneous emission spectrum is improved by

47.45%–53.84% as compared to that of the

conventional AlGaN QW structure. In addition, the

type-II QW structure with x≈0.17 has the largest TE

mode peak intensity in the investigated In-content

range of 0.13–0.23. It can be attributed to the

combined effect of |Mx|2 and fn,c(1-fv,Um) for the

c1–v1, c1–v2, and c1–v3 transitions.

High quality GaN epitaxial growth on -Ga2O3

substrate enabled by self-assembled SiO2

nanospheres State Key Laboratory of Solid-State Lighting, Institute of

Semiconductors, Chinese Academy of Sciences, Beijing

100083, China




Beijing Engineering Research Center for the 3rd

Generation Semiconductor Materials and Application,




To obtain high-quality GaN epitaxial film on (−2 0 1)

-Ga2O3 substrate, periodic SiO2 nanosphere

monolayer was self-assembled followed by

inductively coupled plasma (ICP) etching. This

periodic SiO2 nanosphere patterned Ga2O3

substrate (SiO2-NPGS) enables nanoscale epitaxial

lateral overgrowth (NELOG) of GaN film. Compared

to planar Ga2O3 substrate, SiO2-NPGS shows great

potential for epitaxial GaN with (0 0 0 2) and

(1 0 −1 2) full-width at half-maximum (FWHM)

reduced from 555 to 388 arcsec, and 634 to

356 arcsec, respectively. Raman spectra also

confirm that the as-grown GaN film on SiO2-NPGS is

almost stress-free. The dislocation reduction is also

observed by cross-sectional transmission electron

microscope (TEM). The embedded SiO2-nanosphere

blocks the dislocations and induces the GaN lateral

overgrowth, thus leading to the significant

reduction of the threading dislocation densities.

These findings provide a new way for high quality

stress-free GaN film epitaxial growth on Ga2O3

substrate.

Undoped High-Resistance GaN Buffer Layer for

AlGaN/GaN High-Electron-Mobility Transistors Rzhanov Institute for Semiconductor Physics, Siberian

Branch, Russian Academy of Sciences, Novosibirsk, Russia

National Research University of Electronic Technology

(MIET), Zelenograd, Moscow, Russia

Novosibirsk State Technical University, Novosibirsk,

Russia

Ioffe Physical Technical Institute, Russian Academy of

Sciences, St. Petersburg, Russia

Novosibirsk State University, Novosibirsk, Russia

Technical Physics Letters

https://doi.org/10.1134/S1063785019080108

It is shown that intentionally undoped high-

resistance GaN buffer layers in AlGaN/GaN

heterostructures with high electron mobility for

transistors can be formed by ammonia molecular

beam epitaxy. The GaN growth conditions have

been optimized using calculations of the

background impurity and point defect

concentrations at different ratios of the gallium and

ammonia fluxes.

Growing III–V Semiconductor Heterostructures on

SiC/Si Substrates Ioffe Physical Technical Institute, Russian Academy of

Sciences, St. Petersburg, Russia

Institute for Problems of Mechanical Engineering,

Russian Academy of Sciences, St. Petersburg, Russia

Peter the Great St. Petersburg Polytechnic University, St.

Petersburg, Russia

St. Petersburg National Research University of

Information Technologies, Mechanics, and Optics, St.

Petersburg, Russia

Technical Physics Letters

https://doi.org/10.1134/S1063785019070277

A three-layer heterostructure consisting of AlN

(∼0.72 μm thick), AlGaN (∼ 1.82 μm thick), and GaN

(∼2.2 μm thick) layers has been grown by hydride–

chloride vapor phase epitaxy (HVPE) method on a Si

substrate with a SiC buffer nanolayer. The

heterostructure was studied using scanning

electron microscopy, energy-dispersive X-ray


https://doi.org/10.1134/S1063785019080108

https://doi.org/10.1134/S1063785019070277


spectroscopy, and other techniques. The results

showed that SiC/Si substrates can be used for

growing films of III–V semiconductor compounds by

HVPE at a high rate (~66 μm/h) free of cracks and

with small residual elastic stresses (~160 MPa).

Route to High Hole Mobility in GaN via Reversal of

Crystal-Field Splitting Department of Materials, University of Oxford, Parks

Road, Oxford OX1 3PH, United Kingdom

School of Electrical and Computer Engineering, Cornell

University, Ithaca, New York 14853, USA

Department of Material Science and Engineering, Cornell


PHYSICAL REVIEW LETTERS

https://doi.org/10.1103/PhysRevLett.123.096602

A fundamental obstacle toward the realization of

GaN p-channel transistors is its low hole mobility.

Here we investigate the intrinsic phonon-limited

mobility of electrons and holes in wurtzite GaN

using the ab initio Boltzmann transport formalism,

including all electron-phonon scattering processes

and many-body quasiparticle band structures. We

predict that the hole mobility can be increased by

reversing the sign of the crystal-field splitting in

such a way as to lift the split-off hole states above

the light and heavy holes. We find that a 2% biaxial

tensile strain can increase the hole mobility by

230%, up to a theoretical Hall mobility of 120

cm2/Vs at room temperature and 620cm2/Vs at

100 K.

Hole mobility of strained GaN from first principles Department of Materials, University of Oxford, Parks

Road, Oxford OX1 3PH, United Kingdom

School of Electrical and Computer Engineering, Cornell


Department of Material Science and Engineering, Cornell


PHYSICAL REVIEW B


Nitride semiconductors are ubiquitous in

optoelectronic devices such as LEDs and Blu-Ray

optical disks. A major limitation for further adoption

of GaN in power electronics is its low hole mobility.

In order to address this challenge, here we

investigate the phonon-limited mobility of wurtzite

GaN using the ab initio Boltzmann transport

formalism, including all electron-phonon scattering

processes, spin-orbit coupling, and many-body

quasiparticle band structures. We demonstrate that

the mobility is dominated by acoustic deformation-

potential scattering, and we predict that the hole

mobility can significantly be increased by lifting the

split-off hole states above the light and heavy holes.

This can be achieved by reversing the sign of the

crystal-field splitting via strain or via coherent

excitation of the A1 optical phonon through

ultrafast infrared optical pulses.

Designing Multifunctionality via Assembling

Dissimilar Materials: Epitaxial AlN/ScN

Superlattices Key Laboratory of Computational Physical Sciences

(Ministry of Education), State Key Laboratory of Surface

Physics, and Department of Physics, Fudan University,

Shanghai 200433, China

Collaborative Innovation Center of Advanced

Microstructures, Nanjing 210093, China

Physics Department and Institute for Nanoscience and

Engineering, University of Arkansas, Fayetteville,

Arkansas 72701, USA

School of Physics and Optoelectronic Engineering,

Ludong University, Yantai 264025, China

Laboratoire SPMS, CentraleSupélec/CNRS UMR 8580,

Université Paris-Saclay, 8-10 rue Joliot Curie, 91190 Gif-

sur-Yvette, France

Department of Physics and Astronomy, Rutgers

University, Piscataway, New Jersey 08854, USA

PHYSICAL REVIEW LETTERS


First-principles calculations are performed to

investigate the effect of epitaxial strain on

energetic, structural, electrical, electronic, and

optical properties of 1×1 AlN/ScN superlattices. This

system is predicted to adopt four different strain

regions exhibiting different properties, including

optimization of various physical responses such as

piezoelectricity, electro-optic and elasto-optic

coefficients, and elasticity. Varying the strain

between these four different regions also allows

the creation of an electrical polarization in a

nominally paraelectric material, as a result of a

softening of the lowest optical mode, and even the





control of its magnitude up to a giant value.

Furthermore, it results in an electronic band gap

that cannot only change its nature (direct vs

indirect), but also cover a wide range of the

electromagnetic spectrum from the blue, through

the violet and near ultraviolet, to the middle

ultraviolet. These findings thus point out the

potential of assembling two different materials

inside the same heterostructure to design

multifunctionality and striking phenomena.

Probing Alloy Formation Using Different Excitonic

Species: The Particular Case of InGaN Institute of Physics, École Polytechnique Fédérale de

Lausanne (EPFL), CH-1015 Lausanne, Switzerland

PHYSICAL REVIEW X

https://doi.org/10.1103/PhysRevX.9.031030

Since the early 1960s, alloys are commonly grouped

into two classes that feature either bound states in

the band gap (I) or additional, nondiscrete band

states (II). Consequently, one can observe either

excitons bound to isoelectronic impurities or the

typical band edge emission of a semiconductor that

shifts and broadens with rising isoelectronic doping

concentration. Microscopic parameters for class I

alloys can directly be extracted from

photoluminescence (PL) spectra, whereas any

conclusions drawn for class II alloys usually remain

limited to macroscopic assertions. Nonetheless, we

present a spectroscopic study on exciton

localization in a mixed-crystal alloy (class II) that

allows us to access microscopic alloy parameters. In

order to illustrate our approach, we study bulk

InxGa1−xN epilayers at the onset of alloying

(0≤x≤2.4%) in order to understand their robustness

to point and structural defects. Through an in-depth

PL analysis it is demonstrated how different

excitonic complexes (free, bound, and complex

bound excitons) can serve as a probe to monitor the

dilute limit of class II alloys. From an x-dependent

linewidth analysis we extract the length scales at

which excitons become increasingly localized, i.e.,

their conversion from a free to a bound particle

upon alloy formation. Already at x=2.4% the exciton

diffusion length is reduced to 5.7±1.3nm at a

temperature of 12 K; hence, detrimental exciton

transfer mechanisms toward nonradiative defects

are suppressed. In addition, the associated low-

temperature PL data suggest that a single indium

atom cannot permanently capture an exciton. The

low density of silicon impurities in our samples even

allows studying their local indium-enriched

environment at the scale of the exciton Bohr radius

based on impurity bound excitons. The associated

temperature-dependent PL data reveal an alloying

dependence for the exciton-phonon coupling. Thus,

the formation of the random alloy can not only be

monitored by the emission of various excitonic

complexes, but also more indirectly via the

associated coupling(s) to the phonon bath. Micro-PL

spectra even give access to a probing of silicon

bound excitons embedded in a particular

environment of indium atoms thanks to the

emergence of a series of individual and

energetically sharp emission lines (full width at half

maximum 300μeV). Consequently, the present

study allows us to extract microscopic properties

formerly mostly only accessible for class I alloys.

Three dimensional localization of unintentional

oxygen impurities in gallium nitride Łukasiewicz Research Network-Institute of Electronic

Materials Technology, Wólczy ́nska 133, 01-919

Warsaw, Poland

Chemical Communications

https://doi.org/10.1039/C9CC04707G

Further development of gallium nitride (GaN) based

optoelectronic devices requires in-depth

understanding of defects present in GaN grown on

a sapphire substrate. In this work we present three

dimensional secondary ion mass spectrometry

(SIMS) detection of oxygen. Distribution of these

impurities is not homogeneous and vast majority of

oxygen atoms are agglomerated along pillar-shaped

structures. Defect-selective etching and scanning

electron microscopy imaging complement SIMS

results and reveal that oxygen is predominantly

present along cores of screw and mixed dislocations

which proves their high tendency to be decorated

by oxygen. Negligible amount of oxygen can be

found within a bulk of the material and along edge

dislocations.

https://doi.org/10.1103/PhysRevX.9.031030

https://doi.org/10.1039/C9CC04707G


Integration of BaTiO3/CoFe2O4 multiferroic

heterostructure on GaN semiconductor College of Life Science, Shanxi University, Taiyuan, PR

China

Key Laboratory of Chemical Biology and Molecular

Engineering of Ministry of Education, Institute of

Biotechnology, Shanxi University, Taiyuan, PR China

CrystEngComm

https://doi.org/10.1039/C9CE00932A

Epitaxial integration of BaTiO3 (BTO) /CoFe2O4

(CFO) multiferroic heterostructure directly on GaN

semiconductor was demonstrated using pulsed

laser deposition. Domain matching epitaxy

mechanism was revealed to be (111)[1-10] BTO //

(111)[1-10] CFO // (0002)[11-20] GaN. Spinel CFO

thin film with layer-by-layer growth mode on GaN

could not only be served as ferrimagnetic functional

layer, but also buffer layer, inducing epitaxial

growth of perovskite BTO ferroelectric thin film on

wurtzite GaN by largely reducing lattice mismatch

at BTO/GaN interface. Designed BTO/CFO/GaN

heterostructure displayed high crystallinity, dense

microstructure and good interfacial state. More

importantly, good ferroelectric properties for BTO

layer with remanent polarization of 5.5 μC/cm2,

and magnetic properties for CFO layer with

saturation magnetization of 169 emu/cm3 at room

temperature were also demonstrated. Thus,

epitaxial integration of high performance BTO/CFO

multiferroic heterostructure with GaN could add

more functional freedom degrees for designing

advanced microelectronic devices on GaN

semiconductor platform.

https://doi.org/10.1039/C9CE00932A


PRESS RELEASE Technical and economic information selected by Knowmade

ELECTRONICS

Cambridge GaN Devices co-founder & CEO named RAEng Engineers Trust Young Engineer of the Year SemiconductorToday

Dr Giorgia Longobardi, co-founder & CEO of UK-based Cambridge GaN Devices Ltd (CGD), has been selected by

the Royal Academy of Engineering (RAEng) as one of five young female engineers who have been outstandingly

successful in their respective fields at an early stage of their careers. As an RAEng Engineers Trust Young

Engineer of the Year, she has received a £3000 prize.

Longobardi completed her PhD (focused on the physics of power devices) in 2014, in collaboration with NXP

Semiconductors. She then spent a year in Japan sponsored on a JSPS Postdoctoral Fellowship. Funding of

£75,000 from the UK Engineering and Physical Sciences Research Council (EPSRC) Impact Acceleration Account

(IAA) Follow-on-Fund has enabled Longobardi to work on prototyping a new generation of power devices, to file

two patents, and in 2016 (together with group leader Professor Florin Udrea) to set up Cambridge GaN Devices

(spun out of the Electrical Power and Energy Conversion Group of the University of Cambridge’s Department of

Engineering), which shared first prize in the annual Postdoc Business Plan Competition run jointly by the

Entrepreneurial Postdocs of Cambridge (EPoC) and Cambridge Enterprise.

CGD develops highly efficient power electronics targeting energy savings in applications ranging from power

supplies for consumer electronics to LED drives, data centers and wireless chargers. The firm now employs 10

people and was recently selected as one of the best deep-tech startups to watch by the School of

Entrepreneurship & Innovation in Turin.

Longobardi also has a research fellow in Electronic Engineering at the University of Cambridge’s Gonville & Caius

College, focusing on gallium nitride technologies including sensors and system solutions for efficient power

management.

“I’m very grateful to all the people that have contributed to this prize by supporting my work at both the

Department of Engineering and Gonville & Caius College,” says Longobardi. “A special thank you goes to my

team in Cambridge GaN Devices for their work and commitment towards this amazing venture.”

As an STEM ambassador engaging with school students in countries around the world (including Italy, the UK

and Japan), Longobardi aims to promote STEM subjects to the next generation, especially women.

US Army awards Lockheed Martin contracts for additional GaN-based Q-53 radars and capabilities SemiconductorToday

The US Army recently awarded Lockheed Martin of Bethesda, MD, USA three contracts to produce additional Q-

53 systems and outfit the radar with enhanced capabilities, including extended range and counter unmanned

aerial system (CUAS) surveillance. The flexible architecture of the Army’s most modern radar allows for these

upgrades, which support adaptable growth of the system to address aircraft, drone and other threats in the

future.

http://www.semiconductor-today.com/news_items/2019/aug/cambridge-gan-devices-050819.shtml

http://www.semiconductor-today.com/news_items/2019/aug/lockheed-martin-070819.shtml


In use around the world since 2010, the primary mission of the Q-53 is to protect troops in combat by detecting,

classifying, tracking and identifying the location of enemy indirect fire in either 90 or 360-degree modes.

“The warfighter needs new and improved capabilities. The Q-53 represents a fast path to respond to current

and emerging threats,” says Rick Herodes, director of the Q-53 program at Lockheed Martin. “The flexibility of

the architecture continues to allow the Q-53 to provide capabilities far beyond the original mission and allows

for additional upgrades in the future,” he adds.

• Full-rate production - The Army awarded Lockheed Martin a contract for a third lot of 15 full-rate

production systems. Once this contract is delivered, the Army will own 189 Q-53 systems. The Lot 3

systems will continue to be produced using gallium nitride (GaN) transmit-receive modules, providing

the radar with additional power, reliability and the possibility for enhanced capabilities including

extended range, counterfire target acquisition (CTA) and multi-mission, which delivers simultaneous

CTA and air surveillance.

• Surveillance - Lockheed Martin was also awarded a contract to enhance the Q-53’s CUAS capability. This

true multi-mission capability delivers simultaneous counterfire, CUAS and air surveillance.

• Extended range - Lockheed Martin was also awarded a contract by the Army that will extend the

operating range of the Q-53 system by utilizing recent next-generation technology insertions already

available in the radar.

Lockheed Martin uses an open GaN foundry model, leveraging relationships with commercial suppliers that

utilize the power of the expansive telecoms market to provide military-grade GaN modules while taking

advantage of commercial cost efficiencies.

IGaN launches MPW shuttle program for GaN-on-Si transistors SemiconductorToday

Singapore-based IGSS GaN Pte Ltd (IGaN) – which provides proprietary gallium nitride on silicon (GaN-on-Si)

epitaxial wafer fabrication services for both power and radio frequency (RF) devices – has announced its cost-

effective and quick prototyping multi-project wafer (MPW) shuttle program, as it seeks to advance volume

production in 200mm-diameter silicon substrates.

Enabling customers to tape-out their designs for rapid prototyping, the MPW offers cost reduction through the

expense sharing of masks and wafers with other MPW shuttle program partners. The service leverages the shift

in demand towards GaN devices capable of improving power efficiency conversion up to 50%.

“The industry is ripe for a transition to GaN devices, with various infrastructure coming together making it

conducive to new technologies,” believes president George Wong. “Today, challenges around reliability have

been primarily addressed, paving way for a wider adoption of GaN that is spurred by the increasingly cost-

friendly manufacturing capabilities,” he adds. “This is where IGaN completes the supply chain.”

Ferroelectric gate stack for normally-off gallium nitride power transistors SemiconductorToday

Taiwan’s National Chiao Tung University and Universiti Kebangsaan Malaysia (UKM) have used ferroelectric

materials to create normally-off tri-gate gallium nitride (GaN) metal–insulator–semiconductor high-electron-

mobility transistors (MIS-HEMTs) [Chia-Hsun Wu et al, IEEE Transactions on Electron Devices, published online 8

http://www.semiconductor-today.com/news_items/2019/aug/igan-130819.shtml

http://www.semiconductor-today.com/news_items/2019/aug/nctu-280819.shtml


July 2019]. The researchers claim the lowest reported specific on-resistance for normally-off GaN transistors

with breakdown voltages greater than 650V.

A hafnium oxynitride (HfON) ferroelectric layer in the gate stack was designed to trap charge that shifted the

threshold voltage of the transistor to positive values, giving normally-off behavior – i.e. a low current flow at 0V

gate potential. Normally-off behavior is desired to reduce power consumption, and in power applications to

provide fail-safe operation with simpler circuits. A key trade-off in such devices is between low on-resistance

and high breakdown voltage.

The tri-gate structure improved electrostatic control of current flow in the channel by wrapping the gate stack

around fins etched out of the channel material.

The III-nitride materials were applied to silicon substrates using metal-organic chemical vapor deposition

(MOCVD) to give a 20nm aluminium gallium nitride (Al0.3Ga0.7N) top barrier, 300nm GaN channel and 3μm

carbon-doped GaN buffer. Carbon doping of GaN has been found to make it highly resistive.

The fabricated devices (Figure 1) featured titanium/aluminium/nickel/gold ohmic source-drain contacts,

nitrogen implant planar electrical isolation, inductively coupled plasma (ICP) etched 700nm-long fins/nanowires,

50nm plasma-enhanced CVD silicon nitride passivation, ICP etch of silicon nitride in the 1.5μm gate region,

atomic layer deposition (ALD) of gate dielectric stack layers, 400°C annealing to crystallize the hafnium

zirconium oxide (HfZrO4) in the gate stack, and electron-beam evaporation of the nickel/gold tri-gate.

The gate structure was designed to allow charge trapping in the HfON layer with tunneling through the bottom

6nm Al2O3 layer. A comparison planar structure without nanowire/fin etching was also fabricated. The

overhang of the gate metal on the drain side was designed as a field plate to increase the breakdown voltage.

The nanowire region of the transistor consisted of 119 fins of 140nm height, 100nm width, and 110nm

separation.

The transistors were initialized with 12V applied to the gate, charging up the HfON trapping layer of the gate

stack. The fin structure enables the charges to be closer to the GaN channel, separated by 6nm tunneling oxide

on the sidewalls. This contrasts with the planar structure, and the top of the nanowires, where there is in

addition the 20nm AlGaN barrier, giving a 26nm total.

The closer proximity of the sidewall charge trapping layer increases the threshold voltage of the transistor –

+5.38V shift for the nanowire device, compared with a +3.80V shift for the planar gate with 5V drain bias. These

shifts enabled a positive ‘normally-off’ threshold (Vth) for 1μA/mm drain current of +2.61V in the tri-gate

device, compared with the negative ‘normally-on’ value of -5.28V for the planar transistor.

The team comments: “The tri-gate device demonstrated the highest Vth among the reported normally-off

nanostructured GaN device results, this is due to a high density of negative charges stored in the hybrid

ferroelectric charge trap gate stack.”

The tri-gate finFET also demonstrated better gate control with 73mV/decade subthreshold swing, compared

with 83mV/decade for the planar structure. The hysteresis was slightly higher for the tri-gate transistor at 0.19V,

compared with 0.1V for the planar device. The researchers blamed etch damage, creating interface traps on the

nanowire sidewalls.


Figure 1: (a) Schematic cross section of GaN tri-gate device with hybrid ferroelectric charge trap gate stack. (b)

Schematic cross section of gate dielectric stacks. (c) Top-view scanning electron microscope image of tri-gate

device. (d) High-resolution transmission electron microscope image of single nanowire.


The gate leakage of the tri-gate device was 0.4nA/mm with the gate at 12V. The peak transconductance of the

tri-gate transistor, 177mS/mm, was lower than that of the planar device, 208mS/mm, due to a lower drain

current resulting from removal of more than 50% of the channel width in the fin region.

The maximum drain currents for the planar and tri-gate transistors were 1330mA/mm and 896mA/mm,

respectively. The corresponding gate potentials were 10V and 14V. The on-resistance at these gate potentials at

0.5V drain bias were, respectively, 4.3Ω-mm and 5.0Ω-mm. Again, the removal of channel width by the fin etch

explains the lower drain current and higher on-resistance of the tri-gate transistor.

The breakdown voltage for a leakage current of 1μA/mm was 788V with 0V gate in the tri-gate transistor. To

give an off-state in the planar device, the gate was set at -8V; the resulting breakdown voltages was 738V. The

researchers write: “Higher BV for the tri-gate device is due to the field-plate design associated with the tri-gate

structure.”

The current collapse was investigated with the drain bias off-state stress up to 600V. The off-state time was

10ms. The dynamic on-resistance for 150μs pulses was 1.66x and 1.64x, compared with the DC value (0V drain

stress), for the tri-gate/planar transistors, respectively. The on-state was measured with 12V on the gate and 1V

drain bias.

Figure 2: Benchmarking RON,SP versus BV data of tri-gate device with state-of-the-art normally-off GaN

devices.

In benchmarking breakdown voltage (BV) against specific on-resistance (RON,SP) in other reports (Figure 2), the

researchers comment: “To the best of our knowledge, the proposed tri-gate device shows the lowest RON,SP

among reported normally-off GaN device results with BV >650V.” The RON,SP of the tri-gate transistor was as

low as 0.76Ω-cm2.

One worry for the device would be high-temperature performance at~150°C. The team points out that the

thermal risk of charge detrapping would lead to Vth instability worries. Similar concerns are raised by long-term

gate-bias stress.


Mitsubishi Electric develops first multi-cell GaN-HEMT bonded directly to single-crystal diamond substrate SemiconductorToday

At the International Conference on Solid State Devices and Materials (SSDM) at Nagoya University, Japan (2-5

September), Japan’s Mitsubishi Electric Corp has announced that – in collaboration with the Research Center for

Ubiquitous MEMS and Micro Engineering, National Institute of Advanced Industrial Science and Technology

(AIST) – it has developed what is reckoned to be the first gallium nitride high-electron-mobility transistor (GaN

HEMT) with a multi-cell structure (multiple transistors cells arranged in parallel) bonded directly to a single-

crystal diamond heat-dissipating substrate.

Picture: New GaN-on-diamond HEMT: view from above and cell structure.

Mitsubishi Electric handled the design, manufacture, evaluation and analysis of the GaN-on-diamond HEMT and

AIST developed the direct bonding technology. Part of this achievement is based on results obtained from a

project commissioned by Japan’s New Energy and Industrial Technology Development Organization (NEDO).

In recent years, high-power, high-efficiency GaN HEMTs have been adopted for high-power amplifiers in mobile

communication base stations and satellite communications systems, helping to make such equipment smaller,

lighter and more efficient. However, due to heat generation during high-power operation, the output

performance inherent in GaN HEMTs cannot be realized and their reliability decreases.

Most existing GaN HEMTs that use a diamond substrate for heat dissipation are created using a GaN epitaxial

layer foil from which silicon substrate has been removed and onto which diamond is deposited at high

temperature. HEMTs are then fabricated on the diamond substrate of the flattened GaN wafer. However,

because the thermal expansion coefficients of GaN and diamond are different, the wafer can warp greatly

during the manufacturing process, making it difficult to fabricate large multi-cell GaN HEMTs.

In the latest research a multi-cell GaN HEMT was fabricated then the silicon substrate was removed. The back

surface of the GaN HEMT was then polished to make it thinner and flatter, after which it was bonded directly

onto a diamond substrate using a nano adhesion layer. A multi-cell structure was used for the parallel alignment

of eight transistor cells of a type found in actual products. Finally, a multi-cell GaN-on-diamond HEMT ─ the

world’s first ─ was fabricated using a substrate with high heat dissipation made of single-crystal diamond.

http://www.semiconductor-today.com/news_items/2019/sep/mitsubishi-020919.shtml


Picture: Cross-sectional view of new GaN-on-diamond HEMT.

Using a single-crystal diamond (with high thermal conductivity of 1900W/mK) for superior heat dissipation

suppresses temperature degradation, reducing the temperature rise in the GaN HEMT from 211.1°C to 35.7°C.

This improves output per gate width from 2.8W/mm to 3.1W/mm as well as raising power efficiency from 55.6%

to 65.2%, realizing significant energy conservation.

The new GaN-on-diamond HEMT should be able to improve the power-added efficiency (PAE) of high-power

amplifiers in mobile communication base stations and satellite communications systems, helping to reduce

power consumption. Mitsubishi Electric aims to refine the GaN-on-diamond HEMT prior to its commercial

launch, targeted for 2025.

EPC partners with Solace Power to incorporate eGaN FETs in 250W wireless power platforms SemiconductorToday

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA – which makes enhancement-mode gallium

nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications – is

collaborating with Solace Power, a developer of intelligent wireless power-based solutions featuring proximity

sensing and data, to enable 250W wireless power solutions designed for 5G, aerospace, automotive, medical

and industrial applications. Solace Power’s intelligent wireless platform uses EPC’s 200V eGaN power

transistors. This modular platform shares the same Equus architecture and enables up to 250W of transmitted

power with six degrees of spatial freedom.

“We’re excited to collaborate with EPC to further push the limits of our capacitive wireless power platform and

to deliver previously unachievable solutions with a higher power requirement,” says Solace Power’s CEO

Michael Gotlieb. “Solace focuses on delivering complete, modular systems which are pre-tested for CISPR/FCC

compliance and optimized in-house for rapid development in real-world applications,” he adds. “These new

solutions solve the most important challenges for applications requiring 200W or more.”

For wireless power applications with higher power demands than traditional consumer devices, existing silicon-

based transistors become inefficient, notes EPC. To address this limitation, Solace selected a 200V GaN-based

power transistor from EPC for the 250W solution.

“Wireless power is ready to be incorporated into our daily lives, and the modular platform that Solace Power

has developed, using highly efficient, low-cost GaN transistors, will improve design cycle times and help new

industries implement wireless power quickly and inexpensively,” says EPC’s CEO & co-founder Alex Lidow.

http://www.semiconductor-today.com/news_items/2019/sep/epc-030919.shtml


GaN Versus Silicon For 5G semiengineering

The global race to launch 5G mmWave frequencies could provide a long-anticipated market opportunity for

gallium nitride (GaN) as an alternative to silicon.

GaN is more power-efficient than silicon for 5G RF. In fact, GaN has been the heir apparent to silicon in 5G

power amplifiers for years, especially when it comes to mmWave 5G networks. What makes it so attractive is its

ability to efficiently handle higher voltage in a much smaller area than comparable laterally diffused MOSFETs

(LDMOS) devices. In addition, it can power a much wider range of mmWave frequencies than standard silicon.

“Most of the difference is related to the operating voltage of the transistors, where GaN can be 50V or higher

and 28nm CMOS is perhaps 1.8V,” said Keith Benson, director of RF/microwave amplifier and phased array IC

products at Analog Devices. “In the end, power is voltage times current, and a higher operating voltage makes

high power easier. In regard to comparing GaN versus silicon, in general, that’s a complicated answer as they are

very different. GaN is still expensive from a wafer cost, but the mask cost is far less than cutting-edge CMOS.”

Fig. 1: Comparing power and frequency of different materials in the microwave range, which includes

mmWaves. Source: Analog Devices

That’s a start, but 5G has a host of problems to contend with as it scales from the sub-6GHz range into

millimeter wave technology.

“From a technology standpoint, 5G suffers from attenuation issues, requiring multiple antennae to improve

signal quality using spatial multiplexing techniques. Each antenna requires dedicated RF front-end chipset [and

power amplification],” said Ajit Paranjpe, CTO at Veeco. “Today, GaN is slowly replacing silicon in specific

applications, such as the RF amplifier front-end of 4G/LTE base stations.”

Next-generation designs will open the door to GaN in smaller devices—micro-cells, femto-cells and even smaller

access points, although for different reasons than for higher-powered devices.

“For devices with a lower power load the benefit is in the footprint, not just in board space, as well as the layout

of the antenna,” Paranjpe said. “That’s where GaN offers the best fit because it operates at higher voltages.”

https://semiengineering.com/gan-versus-silicon-for-5g/


With the big boxes, however, the issue is how much power is wasted, not only how much is used, according to

Earl Lum, president of EJL Wireless Research. “Those [power amplifiers] are only maybe 30% or 35% efficient, so

if you put 100 watts into it, you only get to transmit maybe 35 and the other 65 turns into heat.”

At a recent conference in Shanghai, Huawei demonstrated base stations with self-contained liquid-cooling

systems. That may seem like overkill, but the density of chips in base stations generates a significant amount of

heat. Most other OEMs stuck to traditional methods, but there were a lot of abnormally long aluminum fins and

other heat-sink mechanisms on display, Lum said.

Most chipmakers responded by assuming they would be supporting both materials, though a few are pushing

hard on one side or the other.

Qorvo, Wolfspeed, NXP, Sumitomo and other chipmakers — especially those with experience in the microwave

communications market — have promoted GaN for years as a likely successor to LDMOS in 5G base station

power amplifiers (PA) and other applications.

“The data demands driven by 5G and the onset of IoT will require capacity and speeds that, for example,

mmWave technology can deliver,” said Gerhard Wolf, vice president and general manager for the RF product

line at Wolfspeed. “GaN on silicon carbide is the optimal material for mmWave technology because of its high

power density and ability to operate at high frequencies.”

Cree/Wolfspeed is one of the companies making a big bet on the growth of demand for GaN-on-silicon carbide.

In fact, in May it announced plans to invest $1 billion to expand its GaN-on-SiC capacity 30-fold using a

redesigned, 253,000 square-foot facility currently producing 150mm wafers near its Durham, N.C.,

headquarters. “This is in direct answer to the demand for this next-generation technology,” Wolf said. “Today,

communications infrastructure customers are rapidly pre-investing significantly in 5G ramp-up and we’re proud

to be leading the charge on this movement.”

Growth in sales to the defense industry, and to both the 4G and 5G mobile telco market, is forecast to drive

sales of GaN components from $380 million during 2017 to $2 billion by 2024, according to a June report from

Yole Développement. However, the firm noted that the vast majority of PAs in the civilian wireless market will

be silicon.

Sub-6GHz

The same report also predicted “remarkable progress in cost-efficient LDMOS technology,” allowing silicon to

continue to challenge GaN in sub-6GHz, active-antenna and massive-MIMO implementations.

That progress almost certainly would include developing standard-silicon components for mmWave networks,

as longtime RF systems designer Anokiwave has done—while adding functions to reduce the effort of calibrating

phased-array antennas and to reduce power use by as much as a third.

“GaN is fine in isolated uses and a few high-energy applications where it is already popular — LiDAR and radar in

particular,” according to Alastair Upton, Anokiwave’s chief strategy officer, who uses his company’s success at

building phased-array antenna components and controllers from standard LDMOS as evidence GaN is

unnecessary. “We put out our first chips at 28GHz in 2016, and with each generation we’ve gotten orders of

magnitude greater efficiency in size and weight. We continue to drive the cost down at a very rapid pace.”


But Upton noted that, at least for the sub-6GHz version of 5G, GaN chips will have to compete with silicon’s

economies of scale with only marginal additional benefits.

Good designers can get silicon to do astonishing things, but a large amplifier will dissipate heat more slowly than

a small one. So GaN or anything else that can handle the same voltage as silicon in a much smaller space makes

the whole process more power-efficient, said Alex Lidow, co-founder and CEO of GaN power-supply provider

Efficient Power Conversion (EPC).

“Gallium is a better semiconductor than silicon,” Lidow said. “That’s been well known for quite a while.”

GaN traditionally has been more expensive than silicon, and when compared weight-for-weight, there is still a

big difference. But the process of laying down GaN and its components epitaxially on silicon or silicon carbide

brings GaN effectively up to par with silicon, and sometimes can cost slightly less, Lidow said.

Analog Devices’ Benson points to a related trend. “The process technology has finally progressed to a point

where it’s reliable enough to be fielded into systems,” he said. “It took more than 10 years for the fabs to

eliminate many of the issues before it was ready to put into real systems.”

Unavoidable heat issues

Read more

Reduced contact resistance aluminium gallium nitride channel power devices SemiconductorToday

Ohio State University and University of South Carolina in the USA have been developing ohmic contact

structures for use with aluminium gallium nitride (AlGaN)-channel electronic devices [Towhidur Razzak et al,

Appl. Phys. Lett., vol115, p043502, 2019]. AlGaN is an ultrawide-bandgap semiconductor alloy material that

should be able to withstand very large electric fields, enabling high-power and high-voltage applications.

The AlGaN bandgap increases with aluminium content. Pure GaN has been developed for some time for high-

power and high-voltage devices, based on its already wide bandgap of ~3.4eV. For Al contents greater than 0.7,

the AlGaN bandgap exceeds 5.1eV. Breakdown fields greater than 11MV/cm should thus be possible. However,

low resistance to metal contacts is tricky to achieve in high-Al-content AlGaN.

Source-drain contact layers were grown over an Al0.7Ga0.3N channel. Two samples were produced – one (A)

where the aluminium content was graded down to zero (GaN=Al0Ga1N) over 50nm, and the other (B) where the

grading was to Al0.3Ga0.7N over 150nm (Figure 1). The sample B structure enabled a lower silicon doping to be

used to compensate the polarization charge arising from the shallower Al content gradient. The trade-off is

between a low metal-semiconductor contact resistance when the Al content at the surface is low (or zero), and

high contact layer resistance arising from polarization charge effects.

The samples were grown using metal-organic chemical vapor deposition (MOCVD) on AlN-on-sapphire

templates. The source-drain contacts consisted of alloyed titanium/aluminium/nickel/gold. Inductively couple

plasma etched out isolation mesas. Selective recessing 60nm into the channel layer defined the active areas of

the devices. Hall measurements on sample B gave a channel sheet resistance of 5.6kΩ/square, based on

1.8x1013/cm2 sheet carrier density and 56cm2/V-s mobility.

https://semiengineering.com/gan-versus-silicon-for-5g/

http://www.semiconductor-today.com/news_items/2019/sep/ucsb-060919.shtml


Figure 1: (a) Schematic and (b) energy-band diagram of the access region of sample A with silicon-doping

concentration of 8x1018/cm3, and (c) schematic and (d) energy-band diagram of sample B with 3x1018/cm3

silicon concentration.

Sample A had non-linear current-voltage characteristics – indicating incomplete compensation of the negative

polarization charge in the contact layer by the silicon doping. By contrast, sample B’s characteristic was linear.

Sample B’s specific contact resistivity was 3.3x10-5Ω-cm2, according to transfer-length measurements.

The contact layer resistivity in sample B was estimated at 1x10-5Ω-cm2, somewhat higher than reported for

layers grown by molecular beam epitaxy (MBE). The researchers suggest that this could be due to either non-

uniform grading of the contact layer, leading to higher localized polarization charge, and/or non-uniform silicon

incorporation.

Sample A was not subjected to Hall or transfer-length analysis due to the non-linear behavior.

The researchers comment (Figure 2) that “the specific contact resistivity obtained for sample B is the lowest

observed for any MOCVD-grown AlxGa1-xN-channel devices to date for x > 0.5.”

Sample B was used to create metal-semiconductor field-effect transistor (MESFET) structures with

nickel/gold/nickel gates. The gate length was 0.6μm; the source-drain gap was 1.5μm. With 20V drain bias, the

peak transconductance was 38mS/mm; pinch-off occurred at -16V gate potential. The maximum drain current

was 635mA/mm with +2V gate. This value is claimed as “the highest current density achieved to date for

AlxGa1-xN-channel devices with x > 0.5”.


Figure 2: Comparison of specific contact resistivity versus Al-content for state-of-the-art MOCVD-grown

AlxGa1-xN-channel transistors with x greater than 0.5.

Three-terminal breakdown measurements with the gate at -20V showed no breakdown up to +220V gate-drain

potential difference. Combining this with the 0.77μm gate-drain gap gives an average field of 2.86MV/cm -

“almost 3x higher than that exhibited by lateral GaN channel devices with similar dimensions,” the researchers

say.

The team adds: “The breakdown is mainly limited by the gate leakage current which is the primary contributor

to the drain current in the three-terminal breakdown measurement. Thus, the breakdown characteristics can be

further improved by the addition of a gate dielectric such as [aluminium oxide,] Al2O3.”

The researchers conclude: “This demonstration provides a technologically important approach to form low-

resistance contacts to MOCVD-grown ultrawide-bandgap (UWBG) AlxGa1-xN-channel transistors.”

OPTOELECTRONICS

K&S and Rohinni receive initial orders for PIXALUX mini- and micro-LED placement system SemiconductorToday

Singapore-based chip assembly & packaging equipment and materials supplier Kulicke and Soffa Industries Inc

(K&S) and Rohinni LLC of Coeur d’Alene, ID, USA (which has developed a proprietary method for transferring

semiconductor devices) have received initial orders for PIXALUX - K&S’s micro- and mini-LED high-speed die

placement solution that was jointly developed with Rohinni. K&S expects to ship several additional systems

during its current fiscal quarter and anticipates higher-volume market adoption as early as calendar year 2020.

http://www.semiconductor-today.com/news_items/2019/aug/ks-rohanni-020819.shtml


Looking ahead, both K&S and Rohinni anticipate meaningful growth as PIXALUX is increasingly positioned to

enable high-volume and cost-competitive production of LED technology – through a combination of throughput

and accuracy for small-die applications - enabling new forms of backlighting and direct-view LED displays.

Also, at the annual trade show and conference of the Japan Electronics Packaging and Circuits Association (JPCA)

in Tokyo, the PIXALUX placement system was honored with an Equipment of the Year Award.

“The industry recognition from JPCA, our initial system shipments and ongoing customer interest highlight the

unique value PIXALUX is capable of delivering to the broad display market,” says Chan Pin Chong, senior VP at

K&S. “We remain focused on accelerating customer adoption as we prepare to ramp production to high

volume,” he adds.

Customer evaluations of PIXALUX began last fall with systems installed at several manufacturing locations. With

nearly 250 million square meters of flat-panel displays produced annually, the growth potential of emerging

mini- and micro-LED placement technologies is extremely promising, it is reckoned.

Plessey’s micro-LED advisory board gains Apple’s former VP of Macintosh Hardware Systems Engineering SemiconductorToday

UK-based Plessey, which develops embedded micro-LED technology for augmented-reality and mixed-reality

(AR/MR) display applications, has appointed Dr Edward H. Frank to its micro-LED advisory board, as part of the

rapid development of the firm’s micro-LED technology (which promises thinner, brighter, lighter and low-power

displays). Combining the best features of liquid-crystal displays (LCDs) and organic light-emitting diodes (OLEDs),

micro-LEDs represent the fourth-generation flat-panel display technology after plasma, LCD and OLED.

“Ed’s strong and proven history of developing and bringing revolutionary solutions to market makes him an

excellent addition to our advisory board,” reckons Plessey’s co-CEO and CTO Dr Keith Strickland. “His expertise

in delivering innovative silicon and systems, at companies both large and small, will be invaluable as we

continue to provide cutting-edge micro-LED display solutions to AR applications,” he adds.

“Micro-LED display has many advantages such as high brightness, ultra-low power consumption, fast response

time, very high contrast rate, wide colour gamut, long lifetime, environmental stability, high resolution, the

option of flexible backplanes and integration of sensors in the display,” comments Frank. “Its main challenges

are manufacturing complexity and yield issues, all of which Plessey is addressing.”

Previously, Frank was CEO & co-founder of voice-of-the-customer start-up Cloud Parity. Earlier, he served as VP

of Macintosh Hardware Systems Engineering at Apple, as corporate VP of Research and Development at

Broadcom (a broad-based manufacturer of wireless chips used in many Apple devices) and as a Distinguished

Engineer at Sun Microsystems. He is currently on the boards of directors of Analog Devices and Marvell.

Frank earned a BSEE and MSEE from Stanford University, and a Ph.D. in Computer Science from Carnegie Mellon

University, where he is presently vice-chair of its Board of Trustees. He is a member of the US National Academy

of Engineering and is a named inventor on over 50 patents.

http://www.semiconductor-today.com/news_items/2019/aug/plessey-140819.shtml


Automotive LED revenue still growing, with Everlight entering top ten SemiconductorToday

The global automotive market has been showing declines since 2018 amid global trade frictions and economic

recessions, but the penetration rates of LEDs in various major automotive lighting products has continued to

rise, according to the ‘2019 Global Automotive LED Market Report- Passenger Car and Box Truck’ by LEDinside (a

division of TrendForce). Furthermore, new energy cars have a greater demand for LEDs than traditional cars

while boasting faster growth in shipments. This will cause the volume of and revenue for automotive LED

products to maintain modest growth in future years, with automotive LED revenue forecast to reach US$3.17bn

in 2019 while rising at a compound annual growth rate (CAGR) of 7% during 2018-2023.

Automotive LED revenue declining for European and American suppliers, with Asian suppliers performing

brilliantly

“Looking at the automotive LED revenue rankings for major LED package suppliers worldwide, we see Osram

Opto Semiconductors, Nichia and Lumileds still taking the top three in 2018,” says TrendForce analyst Terri

Wang. “However, we may find that, amid declining car markets in both China and the USA, Osram, Lumileds and

other suppliers registered flat growth or small declines in revenue from automotive LED products in 2018.

Japan’s vehicle market gave a rather brilliant performance in 2018, allowing Japanese LED suppliers to post

continual revenue growth. Seoul Semiconductors stood out among Korean suppliers by eagerly meeting the

demands of customers for high power and reliability in the automotive exterior LED lighting sector, giving steady

revenue growth for automotive products.”

TrendForce also notes that Everlight, Cree and other suppliers are actively establishing their place in the OE

market and posted significant growth in revenue. Everlight’s automotive LED products yielded revenue of about

US$48m, placing the firm eighth globally and making it the only Taiwanese supplier in the top ten. Everlight

currently offers mass-produced headlight LEDs, which are poised to penetrate the market consisting of top-tier

European and American vehicle manufacturers. It also plans to develop matrix LED headlights in collaboration

with German manufacturer Hella, to be used in new car models for 2019. Everlight has also released tail-light

mini LED concept products, manufactured using its own small-pitch display components and poised to find

application in 2020. Furthermore, Everlight plans to extend its business to automotive modules, and is already

scheduling the construction of a module production line in its Suzhou plant. We may hence see Everlight

grabbing a bigger portion of the automotive lighting market in the future, says the report.

Headlights growing strongly, with ambient light seeing greater penetration in high-end market

For product development, an increasing variety of LED headlights is seen on the market, with mainstream

suppliers releasing mono-chip or double-chip LEDs for use in low-beam applications. As LEDs move towards

smaller sizes, headlights are being designed with increasing flexibility as the range of features in demand go

beyond lighting to include intelligent systems and even projectors. Revenue and penetration rates for LED

headlights are expected to keep growing in the future years to come.

For automotive interiors, some suppliers are releasing LED products with RGB or better specifications for use in

ambient lights within cars in an attempt to go along with the current intelligent lighting trend. This allows them

to realize effects such as full-color mixing and dynamic ambience. Suppliers of ambient light LEDs mainly

comprise Dominant, Osram, Everlight, Lite-On, and Brightek.

http://www.semiconductor-today.com/news_items/2019/aug/ledinside-190819.shtml


Everlight, for example, released its new 0.2W 2525 LED for use in ambient lights and allows customers to decide

which chip combination (eg RRYY or RGBB) is most suitable for the interior of their cars. These products have a

richer range of colors than that of RGB LEDs.

The emergence of ambient lights may also drive revenue for LEDs used in decorative lights for car interiors.

Currently, full-color LED ambient lighting products are being introduced into high-end car models in the OE

market. As product specifications continue to develop and market demand rises, these products will find

widespread use in mid-range cars in the future, concludes the report.

German court orders permanent injunction and recall of Everlight LED products for infringing Seoul Semiconductor patent SemiconductorToday

South Korean LED maker Seoul Semiconductor Co Ltd has won a patent infringement lawsuit in Germany against

Mouser Electronics, a global distributor of accused LED products – 2835 (2.8mm x 3.5mm) LED packages –

manufactured by Taiwan-based Everlight Electronics Co Ltd.

The District Court of Düsseldorf issued a permanent injunction against sales of the accused Everlight products

and ordered the distributor to recall such products sold after February 2017 from commercial customers. The

decision was issued in the first instance.

The patented technology involved is a Multi-Wavelength Insulation Reflector technology that serves to

efficiently improve light reflectivity from the internal LED structure by attaching a light reflection structure to

the LED chip, which would assure durability and high efficiency of lighting (see Figure A). It has been widely

applied to most cost-effective mid-power LED products, such as those used in lighting, LCD backlights, mobile

phone and automotive applications, where power consumption is 0.5-3W.

In December 2018, Seoul also obtained a permanent injunction against Everlight’s high-power LED products and

a recall was issued for such products sold after 13 July 2012 from commercial customers. This patented

technology serves to efficiently extract light emitted from the internal LED structure by treating LED chip

surfaces (Figure B), and applies to high-power LED products including UV and white LEDs involved in this

litigation. Seoul won all 10 patent litigations against Everlight or its distributor in five major countries including

Europe and Asia (Korea and Japan). Specifically, Everlight filed a patent invalidation action, but the patent office

dismissed it and confirmed the validity of Seoul’s patents.

“To create a fair and competitive market, we will continue enforcement efforts to prevent electronics brands,

manufacturers and distributors from selling products suspected of infringement,” says Seoul’s founder Chung

Hoon Lee. “Only then will others, including young entrepreneurs and small businesses, have a chance to have

http://www.semiconductor-today.com/news_items/2019/aug/seoul-semiconductor-270819.shtml


their talents recognized in the market,” he adds. “We are preparing all legal actions against companies that have

suspicions of infringing our patents or of unlawful access to our trade secrets by luring employees and will

initiate such actions soon.”

III-nitride superluminescent diodes on silicon for displays and communication SemiconductorToday

Researchers in China have developed indium gallium nitride (InGaN) superluminescent diodes (SLDs)

mononlithically integrated on silicon substrates [Jianxun Liu et al, ACS Photonics, published online 9 July 2019].

The team from Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), University of Science and Technology

Beijing, and University of Science and Technology of China, sees opportunities for compact on-chip light sources

for speckle-free displays and visible light communications (VLC).

Figure 1: III-nitride epitaxial structure of SLD, using combinations of aluminium indium gallium nitride

(AlInGaN) alloys.

The researchers used metal-organic chemical vapor deposition (MOCVD) on (111) silicon substrates to create

the III-nitride structure (Figure 1) for the SLD (Figure 2). The index-guided SLD featured a 4μm-wide ridge, which

was J-shaped to suppress optical feedback oscillation in the 800μm-long cavity. Optical feedback runs the risk of

laser action, which is not desired in SLDs. The J-bend of 6° occurred halfway down the cavity. The bend resulted

in a facet that was not perpendicular to the cavity direction, allowing light to escape more easily.

The ridge waveguide and device mesa were formed with plasma etch. The p- and n-electrodes consisted,

respectively, of palladium/platinum/gold and titanium/platinum/gold. After thinning, lapping and chemical

mechanical planarization (CMP), the wafer was cleaved into bars containing 24 devices each. Comparison laser

diodes were produced with straight waveguides. The devices were tested without packaging or facet coating.

The superluminescence of the device was demonstrated from the reduction in linewidth as the current injection

increased from 400mA to 800mA, giving a reduction in full-width at half-maximum (FWHM) from 13.8nm

(102meV) to 3.6nm (26meV), respectively (Figure 3). The main part of the reduction in FWHM occurred around

500mA when the value was 8.5nm (67meV), indicating the main onset of amplified spontaneous emission (ASE).

http://www.semiconductor-today.com/news_items/2019/aug/sinano-290819.shtml


In laser diodes, the reduction in FWHM is sharper, and generally results in linewidths narrower than 1nm – the

fabricated comparison laser diodes had FWHMs of ~0.5nm (3.7meV) above threshold.

Figure 2: (a) Three-dimensional illustration of InGaN-based SLDs grown on silicon with J-shaped ridge

waveguide. (b) Top-view optical microscopy image of bar of InGaN-based SLDs after facet cleavage. (c)

Scanning electron microscope image of cleavage facet. (d) Cross-sectional scanning transmission electron

microscope (STEM) image. Total thickness of epitaxial layer was 5.8μm. (e) Enlarged STEM image of marked

zone in (d).

Figure 3: (a) EL spectra of SLD under various pulsed injection current at room temperature. (b) Peak

wavelength and FWHM as function of injection current. (c) Comparison of EL spectra for SLD below threshold

(100mA), above threshold (800mA), and stimulated emission from LD (250mA) with identical epitaxial design.

As the current through the SLD increased, there was at first a red-shift and then a blue-shift of the

electroluminescence (EL) peak wavelength. The researchers comment: “The observed red-shift under a low


injection current can be attributed to the bandgap narrowing resulting from many-body effects. While the blue-

shift of the EL peak under a high injection current can be explained by combined effects of the band-filling effect

and the carrier-induced screening of the quantum-confined Stark effect.” The quantum-confined Stark effect

refers to the electric field that arises in III-nitride semiconductor heterostructures due to the charge-polarization

of the chemical bonds. The effect tends to shift electron energy levels and to negatively impact electron-hole

recombination into photons.

The transition from spontaneous emission to ASE was also reflected in optical polarization measurements. Even

below threshold, the emissions were dominated by the transverse electric (TE) modes of the waveguide

structure. The degree of polarization, as expressed by the difference in TE and transverse magnetic (TM)

emission relative to the total emission, increased from 84% to 97.6% between 400mA and 600mA injection. The

97.6% value is said to correspond to 20dB polarization extinction ratio (I make it 19dB, but I may have worked

from a different definition).

Comparing SLD and comparison laser diode threshold currents, the former occurred around 550mA, while the

latter achieved lasing around 230mA, less than half the value of the SLD.

The SLD light output power began to saturate at 1100mA injection, and rolled off at 1400mA when about

2.5mW. Although the power was measured under pulsed injection, the saturation and roll-off was attributed to

heating effects. “A significant improvement in optical output power is expected for the SLDs by applying anti-

reflection coating to the cavity facets and adopting proper packaging with good heat dissipation,” the team

writes.

GaN micro-LED market to grow at 43.5% CAGR to 2029, driven by displays SemiconductorToday

The GaN micro-LED market will rise by 33% from $150,000 in 2018 to about $197,000 in 2019, then rise at a

compound annual growth rate (CAGR) of 43.5% during 2019-2029 as the technology promises to offer better

and brighter displays as well as lighting than existing solutions, forecasts a report ‘GaN Micro-LED Market -

Embracing the New-Age Display Technology’ from Future Market Insights.

GaN micro-LEDs have been in research labs for years, and the launch of Samsung’s micro-LED displays (featuring

self-emissive technology and modular capabilities) left consumers curious about the emerging technology.

However, GaN micro-LEDs will soon be a mass-market proposition, as arrays of millions of microscopic LEDs are

set to replace incumbent technologies such as LCDs and OLEDs and penetrate major digital displays markets,

reckons the report.

Despite their extremely high price tag and significant complexity in design, GaN micro-LEDs are gradually finding

acceptance in a wide range of applications, in view of their greater efficiency, improved brightness and lower

power consumption. As the war for supremacy in innovation continues in display markets, GaN micro-LED

players are putting greater emphasis on getting production challenges under control and bringing costs down,

says the report.

Sensing the application potential of GaN micro-LEDs in newer models of TVs, smartwatches, augmented reality

(AR) devices and head-mounted systems such as Google Glass, stakeholders are investing strongly in R&D and

deepening their collaborations with technology solution providers.

http://www.semiconductor-today.com/news_items/2019/sep/futuremarketinsights-020919.shtml


Mid-power micro-LEDs for lighting applications to capture robust share

The consumption of mid-power GaN micro-LEDs, which accounted for ~75% share in 2018, will become

mainstream for lighting applications in the years ahead, forecasts the report. However, a significant proportion

of costs goes into packaging, limiting the advantage of reducing overall costs. On the other hand, demand for

low-power micro-LEDs is likely to gain significant traction in the future, in view of maintaining full brightness

without the loss of noticeable display brightness over the entire illumination time.

Greater demand for GaN micro-LED displays will continue to influence the growth strategies, accounting for

about 79% share in 2018. Growth will continue to be driven by demand for visual aspects in modern-day

devices, the increasing need for high luminance in small formats for near-to-eye display devices, and demand

for high resolution and efficient luminance in battery-powered consumer electronics, the report notes.

Market gains underpinned by innovations in sports & entertainment

In recent years, great potential for GaN micro-LED application has been identified in the sports & entertainment

space, due to a spike in the number of video-streaming services, the rapid innovations in television to enhance

the viewing experience, and increased penetration of new-generation video-gaming products and accessories,

says the report.

While consumer electronics are likely to account for the major share of manufacturers’ bottom lines, capitalizing

on the ever-expanding sports & entertainment space will remain a key focus of market players.

On the other hand, the consumption of GaN micro-LEDs by the automotive industry will grow by about 39%

year-on-year in 2019, backed by the emergence of ‘in-car ambience’ and ‘auto-infotainment’ trends leading to

innovations in automotive displays units as well as interior automotive lighting.

North America in vanguard; APEJ to outdo European market

Accounting for 26% share in 2018, North America is expected to remain at the forefront of GaN micro-LED

market. The European market is likely to lose second position in the foreseeable future to the Asia Pacific (APEJ,

excluding Japan), where many players are continuing to demonstrate progress and making the latest

breakthroughs in GaN micro-LED technology.

Unprecedented evolution in the number of industry verticals has pushed stakeholders to redefine their growth

strategies to retain and attract new categories of customer, states the report. In addition to focusing entirely on

new technology while curtailing the launch of conventional solutions, stakeholders are centered on

collaborating with research institutes in order to synchronize their advances, the report concludes.

Nanosys Signs License For Control Of Yissum QD Patents CompoundSemiconductor

Nanosys, a quantum dot company, has announced that it has signed an exclusive license agreement with

Yissum, the Technology Transfer Company of The Hebrew University of Jerusalem for a worldwide patent

portfolio related to quantum dot technology.

Under the terms of the agreement, Yissum will grant Nanosys an exclusive, worldwide, sub-licensable, royalty-

bearing license to its patented technology for quantum dots in display, lighting and healthcare applications.

https://compoundsemiconductor.net/article/108339/Nanosys_Signs_License_for_Control_of_Yissum_QD_Patents


The technology includes key patents related to the base composition of heavy metal free quantum dots as well

as novel material structures such as nanorods that may enable improved photoelectronic performance for a

variety of future applications.

Representing 15 years of research and development by Uri Banin from the Institute of Chemistry and the Center

for Nanoscience and Nanotechnology at the Hebrew University, the licensed intellectual property includes over

60 issued and pending patents around the world across about a dozen patent families. Yissum's Quantum Dot

portfolio has an average lifetime of over ten years with many patents not expiring until 2030 and beyond.

Nanosys' QD IP portfolio includes more than 450 patents and patent applications worldwide, including the US,

Europe, Japan, Korea, Taiwan, China, India, Australia, Brazil, and Israel.

Yaron Daniely, CEO and president of Yissum, said: "Nanosys is an excellent example of a leading company

investing in research results rooted in the strong nanotechnology and materials research at the Hebrew

University. This agreement will allow the continued development and commercialisation of promising

innovation coming out of our institution, in line with Yissum's mission of creating opportunities for academic

knowledge and technology transfer worldwide."

"Yissum's quantum dot patent portfolio comes from a leading university with one of the strongest quantum dot

research teams in the world over the last two decades," said Charlie Hotz, VP of R&D at Nanosys. "This

transaction significantly extends Nanosys' patent portfolio, enabling us to expand the foundational coverage for

the range of heavy metal free Quantum Dot technologies and materials that we offer to our customers and

accelerate the growth of the quantum dot marketplace."

AquiSense’s UV-C LED technology playing increasing role in aerospace projects SemiconductorToday

Nikkiso Group company AquiSense Technologies LLC of Erlanger, KY, USA (which designs and manufactures

water, air and surface disinfection systems based on UV-C LEDs) says that it has participated in ten distinct

aerospace projects.

http://www.semiconductor-today.com/news_items/2019/sep/aquisense-100919.shtml


In 2015 the firm was selected to participate in BIOWYSE, a European Union Horizon 2020 project dedicated to

designing and testing a water monitoring and treatment system for next-generation manned space stations.

Since then, several other aerospace projects have sought water treatment technology from AquiSense, including

product design and hardware supply to both private space companies (such as Bigelow Aerospace, Thales Alenia

Space Italia, KBR Wyle, and Aero Sekur) and various NASA groups (including those at the Jet Propulsion

Laboratory, Johnson Space Center, and Marshall Space Flight Center). These projects range from keeping growth

systems clean in space-bound greenhouses, to decreasing the maintenance burden from nuisance biofilm

formation in enclosed systems, to disinfecting the water that astronauts drink on the International Space Station

(ISS).

“The driving factor for all of these projects is our leading knowledge of system design and the application of UV-

C LEDs in unique environments,” says Rich Simons Ph.D., product development scientist at AquiSense

Technologies Europe. “These types of applications are exciting for us as they drive innovation for our technology

and allow us to better understand the possibilities and limits of UV-C LED disinfection.”

OTHER

Osram clears way for ams takeover offer of €38.50 per share SemiconductorToday

The managing board and supervisory board of Osram GmbH of Munich, Germany have waived the existing

standstill agreement with ams AG of Premstaetten, Austria (which designs and makes high-performance sensor

and analog solutions) and signed a cooperation agreement, clearing the way for a voluntary public takeover

offer by ams. The offer, which is expected to be valid until the beginning of October, amounts to €38.50 in cash

per share, with a minimum acceptance level of 70%.

“Our shareholders now have two offers on the table, allowing them to choose between the different business

concepts,” says Olaf Berlien, CEO of OSRAM Licht AG.

In early July, Osram’s managing board and supervisory board announced support for a legally binding public

takeover offer (of €35 in cash per share) from a bidding consortium composed of US-based firms Bain Capital

and The Carlyle Group, as well as signing an investor agreement that included comprehensive commitments.

“We are proud to have made brave, strategically right decisions in an extremely difficult market environment

over the past few years. The interest shown by several bidders, both from the private equity sector and the

industry, is testimony for this,” Berlien says.

Osram says that, in addition to providing a takeover offer with a secured financing for shareholders, it is

important to its managing board and supervisory board that employee interests are safeguarded, so the

cooperation agreement with ams thus provides commitments for employees and essential parts of the

company. ams has also committed to maintaining existing collective agreements, works agreements and similar

arrangements. Existing pension plans shall also be fully retained. Munich would become co-headquarters, with

global central functions. Osram would continue to operate under its current name and exist as a brand following

the takeover.

http://www.semiconductor-today.com/news_items/2019/aug/osram-230819.shtml


Osram will also give ams further opportunity to convince its managing board and supervisory board of the

business orientation, global location strategy and integration concept. For various reasons, it has not yet been

possible to reach an adequate understanding on these issues. In particular, integration of an industrial group

with revenue of more than €3.8bn (in fiscal year 2018) and a presence in about 70 countries by a significantly

smaller company represents a challenging task, says Osram.

Osram says that its consequent transformation into a high-tech photonics company remains the only viable way

for it to secure growth over the medium and long term. Osram will hence continue to focus on moving in this

direction.

The offer document of ams still needs to be reviewed and approved by the German Federal Financial

Supervisory Authority (BaFin) in accordance with the provisions of the German Securities Acquisition and

Takeover Act (WpÜG).

GLOBALFOUNDRIES Files Patent Infringement Lawsuits Against TSMC In the U.S. and Germany GlobeNewsWire

Santa Clara, Calif., Aug. 26, 2019 (GLOBE NEWSWIRE) -- GLOBALFOUNDRIES (GF), the world’s leading specialty

foundry based in the United States, today filed multiple lawsuits in the U.S. and Germany alleging that

semiconductor manufacturing technologies used by Taiwan Semiconductor Manufacturing Company Ltd.

(TSMC) infringe 16 GF patents. The lawsuits were filed today in the U.S. International Trade Commission (ITC),

the U.S. Federal District Courts in the Districts of Delaware and the Western District of Texas, and the Regional

Courts of Dusseldorf and Mannheim in Germany.

In filing the lawsuits, GF seeks orders that will prevent semiconductors produced with the infringing technology

by Taiwan-based TSMC, the dominant semiconductor manufacturer, from being imported into the U.S. and

Germany. These lawsuits require GF to name certain major customers of TSMC and downstream electronics

companies, who, in most cases, are the actual importers of the products that incorporate the infringing TSMC

technology. GF also seeks significant damages from TSMC based on TSMC’s unlawful use of GF’s proprietary

technology in its tens of billions of dollars of sales.

“While semiconductor manufacturing has continued to shift to Asia, GF has bucked the trend by investing

heavily in the American and European semiconductor industries, spending more than $15 billion dollars in the

last decade in the U.S. and more than $6 billion in Europe's largest semiconductor manufacturing fabrication

facility. These lawsuits are aimed at protecting those investments and the US and European-based innovation

that powers them,” said Gregg Bartlett, senior vice president, engineering and technology at GF. “For years,

while we have been devoting billions of dollars to domestic research and development, TSMC has been

unlawfully reaping the benefits of our investments. This action is critical to halt Taiwan Semiconductor’s

unlawful use of our vital assets and to safeguard the American and European manufacturing base.”

GF is filing these lawsuits to protect its investments, assets and intellectual property, which will help to ensure

that semiconductor manufacturing remains a competitive industry for the benefit of its clients.

Eta launches polished epi-ready 100mm n-type GaN wafers SemiconductorToday

Eta Research of Lingang Free Trade Zone, Shanghai, China, which was founded in 2015 to develop free-standing

gallium nitride (GaN) wafers, is now selling n-type 100mm GaN wafers with an epitaxial-ready polish.

https://www.globenewswire.com/news-release/2019/08/26/1906537/0/en/GLOBALFOUNDRIES-Files-Patent-Infringement-Lawsuits-Against-TSMC-In-the-U-S-and-Germany.html

http://www.semiconductor-today.com/news_items/2019/sep/eta-040919.shtml


Eta has completed the R&D necessary to commercialize GaN wafers, resulting in its unique hydride vapor phase

epitaxy (HVPE) equipment, wafer separation process, and polishing process. In 2018, the firm demonstrated as-

grown GaN wafers of 100mm diameter that can be cut to 2” and 3” wafers as the finished size. This year it

developed almost 5” as-grown GaN wafers that can be cut and processed into 100mm wafers.

Eta says that it places a strong emphasis on the importance of the crystal quality and lattice curvature. The

typical rocking curve full-width half-maximum (FWHM) of the as-grown wafers is 50-60 arcsec for both the (002)

and (102) reflections. The threading dislocation density has been measured as 1E6/cm2 based on the cathodo-

luminescence (CL) of polished wafers. The lattice curvature is important as a measure of the offcut variation

across the wafer. The center point offcut is specified at 0.35° toward the GaN m-direction, and that can be

modified according to the customer’s requirement. The lattice curvature radius is greater than 10m, with the

target around 30m or larger.

The firm has developed its own polishing process for GaN, resulting in atomic force microscope (AFM) average

roughness over 10μm images of <0.3nm. It has grown MOCVD GaN epilayers and device structures on the GaN

wafers. The MOCVD-grown layers are said to show good surface morphology and have x-ray diffraction (XRD)

rocking curve FWHMs similar to that of the substrate.

Currently, small quantities of 100mm GaN wafers are for sale, as well as 2” and 3” wafers. At the end of 2019,

more HVPE capacity will be brought online in the new production factory located in Tongling, Anhui Province,

China. The firm expects to be able to supply high-volume customers in the near future. Further, working with

their epitaxial growth partners, Eta can offer GaN wafers with MOCVD epilayers for interested customers.


PATENT APPLICATIONS

More than 320 new patent families (inventions) were published in August 2019.

Other patent applicants Xiangneng Hualei Optoelectronic Corppration, 13th Research Institute of China Electronics Technology, Akoustis, Denso, Forschungsverbund Berlin EV, Fuzhou University, Guangdong Institute of Semiconductor Industrial Technology, Hengshan Jiacheng New Material, HRL Laboratories, Huainan Normal University, IBM, Jiangxi Qianzhao Optoelectronic, Kyocera, Maanshan Jiesheng Semiconductor, Nanjing University, Nanjing University of Posts & Telecommunications, Panasonic, Pinger Semiconductor, Sanan Integrated Circuit Manufacturing, Shandong University, Shanghaitech University, Shenzhen Original Digital, Sumitomo Chemical, Sumitomo Electric Industries, Suzhou Institute of Nano Technology & Nano Bionics Chinese Academy of Sciences, Toyoda Gosei, Unilumin, Xi'an Jiaotong University, Xiangtan University, Zhejiang Super Lighting Electric Appliance, Administrators of The Tulane Educational Fund D Tulane University, Advanced Semiconductor Engineering, Air Liquide, Analog Devices, Anhui Huajing Microelectronics Materials, Ansys, Anyang Normal University, Asahi Kasei, Ausnutria Dairy, Beijing Ainfo Technology, Beijing Dahua Hengwwei Communication Technology, Beijing Institute of Graphite, Beijing Institute of Nanoenergy & Nanosystems, Beijing Juci Technology, Biological Innovation & Optimization Systems, BOE Technology, Changxing Kedi LED, Chengdu BOE Optoelectronics Tecnhology, Chengdu Changdao Technology, China Communication Microelectronics Technology, Chongqing University, Chonnam National University, Cook, Cornell University, Cree, Dai Nippon Printing, Dalian University of Technology,


Datang Terminal Technology, Dialog Semiconductor, Dongguan Institute of Opto Electronics Peking University, Dowa Holdings, Duesenfeld, Episky, Eyun Pharm, Federalnoe Gosudarstvennoe Byudzhetnoe Obrazovatelnoe Uchrezhdenie Vysshego Obrazovaniya Tomskij Gosudarstvennyj Arkhitekturno, First Semiconductor Materials, Florida International University, Ford Global Technologies, Foshan Guoxing Semiconductor Technology, Foshan Huayu Equity Investment Partnership, Fudan University, Fuji Electric, Fujitsu.

Notable new patent applications

Highly scaled linear GaN HEMT structures Publication Number: US20190252535, WO2019/160598 Patent Applicant: HRL Laboratories

A transistor includes a substrate, a channel layer coupled to the substrate, a source electrode coupled to the channel layer, a drain electrode coupled to the channel layer, and a gate electrode coupled to the channel layer between the source electrode and the drain electrode. The gate electrode has a length dimension of less than 50 nanometers near the channel layer, and the channel layer includes at least a first GaN layer and a first graded AlGaN layer on the first GaN layer.

High electron mobility transistor and method for manufacturing high electron mobility transistor Publication Number: US20190259866, WO2019/163163 Patent Applicant: Mitsubishi Electric A high electron mobility transistor (HEMT) includes a channel semiconductor structure (160) including a stack of layers arranged on top of each other in an order of magnitudes of the polarization of materials of the layers to form multiple carrier channels at heterojunctions formed by each pair of layers in the stack. The stack of layers includes a first layer and a second layer. The magnitude of polarization of the first layer is greater than the magnitude of polarization of the second layer arranged in the stack below the first layer, and the width of the first layer is less than the width of the second layer to form a staircase profile of the channel semiconductor structure. The HEMT includes a source semiconductor structure (140) including a heavily doped semiconductor material, a drain semiconductor structure (150) including the heavily doped semiconductor material. The HEMT includes source (110), drain (120), and gate electrodes (130) to modulate the conductivity of the carrier channels. The gate electrode has a staircase shape having trends and risers tracking the staircase profile of the channel semiconductor structure.

https://sobjprd.questel.fr/sobj/servlet/get_pds/US20190252535A1.pdf?userid=QPRK1002&type=0&pdfid=89785932&ekey=993



Method and system for forming doped regions by diffusion in gallium nitride materials Publication Number: US20190252186, WO2019/157384 Patent Applicant: Qromis

A method of forming doped regions by diffusion in gallium nitride materials includes providing a substrate structure including a gallium nitride layer and forming a mask on the gallium nitride layer. The mask exposes one or more portions of a top surface of the gallium nitride layer. The method also includes depositing a magnesium-containing gallium nitride layer on the one or more portions of the top surface of the gallium nitride layer and concurrently with depositing the magnesium-containing gallium nitride layer, forming one or more magnesium-doped regions in the gallium nitride layer by diffusing magnesium into the gallium nitride layer through the one or more portions. The magnesium-containing gallium nitride layer provides a source of magnesium dopants. The method further includes removing the magnesium-containing gallium nitride layer and removing the mask.

Nitride semiconductor device Publication Number: US20190237551, JP2019134041 Patent Applicant: Rohm

A nitride semiconductor device 1 includes a first nitride semiconductor layer 4, constituting an electron transit layer, a second nitride semiconductor layer 5, formed on the first nitride semiconductor layer 4and constituting an electron supply layer, a nitride semiconductor gate layer 6, disposed on the second nitride semiconductor layer 5 and containing an acceptor type impurity, a metal film 7, formed on the nitride semiconductor gate layer 6, and a gate pad 23, connected to the metal film 7 via a gate insulating film 8 having a first surface and a second surface, the first surface of the gate insulating film 8 is electrically connected directly or via a metal to the metal film 7, and the second surface of the gate insulating film 8 is electrically connected directly or via a metal to the gate pad 23.




Nitride semiconductor device and nitride semiconductor package Publication Number: US20180061975, JP2018157177 Patent Applicant: Rohm

Provided is a nitride semiconductor device 3 including a GaN electron transit layer 13, an AlGaN electron supply layer 14 in contact with the electron transit layer 13, a gate layer 15, formed selectively on the electron supply layer 14 and constituted of a nitride semiconductor composition effectively not containing an acceptor type impurity, and a gate electrode 16, formed on the gate layer 15, and satisfying the following formula (1):

Etched spin-qubit for high temperature operation Publication Number: US10387792 Patent Applicant: HRL Laboratories A device for storing and/or transferring quantum data. The device has a plurality of elongate semiconductor structures arranged in side by said with each elongate semiconductor structure having a quantum well layer of one semiconductor material disposed between upper and lower layers of a different semiconductor material which share the same or essentially the same crystalline structure as that of the quantum well layer. Neighboring ones of the elongate semiconductor structures share a region forming a constriction between the neighboring ones of the elongate semiconductor structures. Also disclosed is a a method of adjusting exchange coupling between laterally coupled quantum wells in a quantum device having sidewalls, the method including: defining the sidewalls by etching a crystalline structure along lattice planes of said crystalline structure, the crystalline structure, after the sidewalls are etched, having a corrugated shaped with protuberances and grooves on opposing major surfaces thereof, and controlling a ratio of the distances (i) between opposing grooves on the opposing major surfaces of the crystalline structure and (ii) between opposing protuberances on the opposing major surfaces of the crystalline structure.


https://sobjprd.questel.fr/sobj/servlet/get_pds/US10387792B1.pdf?userid=QPRK1002&type=0&pdfid=89885373&ekey=996


Method of reducing semiconductor substrate surface unevenness Publication Number: WO2019/164449 Patent Applicant: MIT

Disclosed is a method of reducing surface unevenness of a semiconductor wafer (100). In a preferred embodiment, the method comprises: removing a portion of a deposited layer and a protective layer thereon using a first slurry to provide an intermediate surface (1123). In the described embodiment, the deposited layer includes an epitaxial layer (112) and the protective layer includes a first dielectric layer (113). The first slurry includes particles with a hardness level the same as or exceeding that of the epitaxial layer (112). A slurry for use in wafer fabrication for reducing surface unevenness of a semiconductor wafer is also disclosed.

Semiconductor device Publication Number: WO2019/163075 Patent Applicant: Mitsubishi Electric This semiconductor device comprises: a support substrate having a first main surface and a second main surface; a first GaN layer of a first electroconductive type provided on the first main surface side of the support substrate; a second GaN layer of the first electric conduction type provided on the first GaN layer; an AlxGa1-xN (0 < x < 1) layer provided on the second GaN layer; a third GaN layer of a second electroconductive type provided on the AlxGa1-xN (0 < x < 1) layer; a fourth GaN layer of the first electroconductive type provided on the third GaN layer; an insulation film covering at least the top of the fourth GaN layer; a trench gate reaching from the upper surface of the fourth GaN layer into the second GaN layer; a gate electrode provided in the trench gate through a gate insulation film; a first main electrode connected to the third GaN layer; and a second main electrode forming a pair with the first main electrode wherein the donor concentration in the third GaN layer is lower than the donor concentration in the fourth GaN layer.

https://sobjprd.questel.fr/sobj/servlet/get_pds/WO2019164449A1.pdf?userid=QPRK1002&type=0&pdfid=90084401&ekey=916



Electronic device with 2-dimensional electron gas between polar-oriented rare-earth oxide layer grown over a semiconductor Publication Number: WO2019/159001 Patent Applicant: IQE Layered structures described herein include electronic devices with 2- dimensional electron gas between polar-oriented cubic rare-earth oxide layers on a non-polar semiconductor. Layered structure includes a semiconductor device, comprising a III-N layer or rare-earth layer, a polar rare-earth oxide layer grown over the III-N layer or rare-earth layer, a gate terminal deposited or grown over the polar rare-earth oxide layer, a source terminal that is deposited or epitaxially grown over the layer, and a drain terminal that is deposited or grown over the layer.

Semiconductor device and method for manufacturing semiconductor device Publication Number: WO2019/151277, JP2019134164 Patent Applicant: Denso, Toyota Motor This semiconductor device comprises: a first film (32a, 132a) laminated over a nitride semiconductor; a second film (32b, 132b) laminated over the first film; a third film (32c, 132c) laminated over the second film; and a gate electrode (34, 134) laminated over the third film. The first film, the second film, the third film and the gate electrode constitute an insulated gate structure. The interface trap formed in the interface between the first film and the nitride semiconductor is small. The second film is a polycrystal, having a resistance of 1 × 109 (Ωcm) or greater. The third film is an insulator having a breakdown field strength of 6 (MV/cm) or greater.

Low-dislocation bulk gan crystal and method of fabricating same Publication Number: US20190249333, WO2019/157313 Patent Applicant: SixPoint Materials

GaN wafers and bulk crystal have dislocation density approximately 1/10 of dislocation density of seed used to form the bulk crystal and wafers. Masks are formed selectively on GaN seed dislocations, and new GaN grown on the seed has fewer dislocations and often 1/10 or less of dislocations present in seed.





Deep ultraviolet LED and production method for same Publication Number: WO2019/146737 Patent Applicant: Dai Nippon Printing, Dowa, Toshiba, Ulvac A deep ultraviolet LED that has a design wavelength of λ. The deep ultraviolet LED is characterized by including, in order from the side opposite a sapphire substrate, a reflecting electrode layer (Au), a metal layer (Ni), a p-type GaN contact layer, a P-Block layer that comprises a p-type AlGaN layer and has a film thickness of 52–56 nm, an i-guide layer that comprises an AlN layer, a multi quantum well layer, an n-type AlGaN contact layer, a u-type AlGaN layer, an AlN template, and the sapphire substrate. The deep ultraviolet LED is also characterized by including a reflective two-dimensional photonic crystal periodic structure that includes a plurality of holes and is provided from the interface between the metal layer and the p-type GaN contact layer within the thickness-direction range of the p-type GaN contact layer but does not cross the interface between the p-type GaN contact layer and the P-Block layer. The deep ultraviolet LED is also characterized in that the distance from sapphire-substrate-side end surfaces of the holes to the interface between the multi quantum well layer and the i-guide layer satisfies λ/2n1Dneff in the vertical direction and is 53–57 nm. The deep ultraviolet LED is also characterized in that the reflective two-dimensional photonic crystal periodic structure has photonic gaps that open toward a TE polarization component. The deep ultraviolet LED is also characterized in that the period a of the reflective two-dimensional photonic crystal periodic structure satisfies the Bragg condition with respect to light of the design wavelength λ, in that the order m of the Bragg conditional expression mλ/n2Deff=2a (m being the order, λ being the design wavelength, n2Deff being the effective refractive index of the two-dimensional photonic crystal, and a being the period of the two-dimensional photonic crystal) satisfies 2≤m≤4, and in that, when the radius of the holes is R, 0.30≤R/a≤0.40.

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