GaN Technology for Optoelectronics & Electronics...application of the nanoporous GaN-based TP structure for optical sensing. Three-dimensional metal–semiconductor–metal AlN deep-ultraviolet

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GANEXT Newsletter No. 06 July 2020

GaN Technology for Optoelectronics & Electronics

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GANEXT | GaN Technology for Optoelectronics & Electronics Newsletter No. 06 | 2

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IMPORTANT NOTE: The end of GaNeX Cluster of Excellence program (Labex 2012-2019) was scheduled on December 2019. However, the French government decided to expand the labex program for five additional years, in order to further strengthen the synergy between French academic research organizations and industrial players in the field of GaN optoelectronics and electronics. Therefore, GANEXT Cluster of Excellence program will replace and succeed GaNeX for the next five years (2020-2024). Accordingly, the GANEXT newsletter will follow and adapt to the new program, focusing on scientific publications, patent applications and press releases related to optoelectronics (LED, µ-LED, laser, photonics, etc.) and electronics (power, RF, advanced electronics, etc.), ruling out publications which are not related to one of these two families of applications. For instance, publications dealing with MEMS, sensors, photovoltaics, nanostructures, semi-polar and non-polar materials, fundamental physics, etc. that do not obviously relate to optoelectronic or electronic applications will not be included in the GANEXT newsletter. Besides, a panel of GANEXT experts will continue to interact with Knowmade team in order to select the most relevant publications of the month, consistently with GANEXT’s ongoing projects.

TABLE OF CONTENTS

METHODOLOGY ........................................................................................................... 3

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

OPTOELECTRONICS ....................................................................................................... 4

ELECTRONICS .............................................................................................................. 20

PRESS RELEASE........................................................................................................... 37

PATENT APPLICATIONS .............................................................................................. 73


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METHODOLOGY


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SCIENTIFIC PUBLICATIONS Selection of new scientific articles

OPTOELECTRONICS Group leader: Bruno Gayral (CEA)

Information selected by Julien Brault (CNRS-CRHEA), Maria Tchernycheva (CNRS-C2N) and Thierry Guillet (CNRS-L2C) Nanoscale Structural and Emission Properties within

“Russian Doll”‐Type InGaN/AlGaN Quantum Wells Canadian Centre for Electron Microscopy and Department

of Materials Science and Engineering, McMaster University,

Main Street West, Hamilton, Ontario, L8S4M1 Canada

Department of Physics, McGill University, 3480 University

Street, Montreal, Quebec, H3A0E9 Canada

Beijing Key Laboratory of Nanophotonics and Ultrafine

Optoelectronic Systems, School of Physics, Beijing Institute

of Technology, 5 Zhongguancun South Street, Beijing,

100081 China

Delmic BV, Kanaalweg 4, Delft, 2628EB The Netherlands

Optic & Electronic Component Material Center, Korea

Institute of Ceramic Engineering & Technology, Jinju, 52851

Republic of Korea

School of Physics and Engineering, Zhengzhou University,

Daxue Road 75, Zhengzhou, 450052 China

Department of Electrical Engineering and Computer

Science, University of Michigan, 1301 Beal Avenue, Ann

Arbor, MI, 48109 USA

Canadian Light Source, 44 Innovation Boulevard, Saskatoon,

Saskatchewan, S7N2V3 Canada

Advanced Optical Materials

https://doi.org/10.1002/adom.202000481

Due to the increasing desire for nanoscale

optoelectronic devices with green light emission

capability and high efficiency, ternary III‐N‐based

nanorods are extensively studied. Many efforts have

been taken on the planar device configuration, which

lead to unavoided defects and strains. With selective‐

area molecular‐beam epitaxy, new “Russian Doll”‐type

InGaN/AlGaN quantum wells (QWs) have been

developed, which could largely alleviate this issue. This

work combines multiple nanoscale characterization

methods and k∙p theory calculations so that the

crystalline structure, chemical compositions, strain

effects, and light emission properties can be

quantitatively correlated and understood. The 3D

structure and atomic composition of these QWs are

retrieved with transmission electron microscopy and

atom probe tomography while their green light

emission has been demonstrated with room‐

temperature cathodoluminescence experiments. k∙p

theory calculations, with the consideration of strain

effects, are used to derive the light emission

characteristics that are compared with the local

measurements. Thus, the structural properties of the

newly designed nanorods are quantitatively

characterized and the relationship with their

outstanding optical properties is described. This

combined approach provides an innovative way for

analyzing nano‐optical‐devices and new strategies for

the structure design of light‐emitting diodes.

Phosphor-free single chip GaN-based white light

emitting diodes with a moderate color rendering

index and significantly enhanced communications

bandwidth State Key Laboratory of High Performance Complex

Manufacturing, College of Mechanical and Electrical

Engineering, Central South University, Changsha 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,

Beijing 101408, China

State Key Laboratory of Integrated Optoelectronics,

Institute of Semiconductors, Chinese Academy of Sciences,


Photonics Research

https://doi.org/10.1364/PRJ.392046

To achieve high quality lighting and visible light

communication (VLC) simultaneously, GaN based

white light emitting diodes (WLEDs) oriented for

lighting in VLC has attracted great interest. However,

the overall bandwidth of conventional phosphor

converted WLEDs is limited by the long lifetime of

phosphor, the slow Stokes transfer process, the

resistance-capacitance (RC) time delay, and the

quantum-confined Stark effect (QCSE). Here by

adopting a self-assembled InGaN quantum dots (QDs)

structure, we have fabricated phosphor-free single

https://doi.org/10.1002/adom.202000481https://doi.org/10.1364/PRJ.392046


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chip WLEDs with tunable correlated color temperature

(CCT, from 1600 K to 6000 K), a broadband spectrum,

a moderate color rendering index (CRI) of 75, and a

significantly improved modulation bandwidth

(maximum of 150 MHz) at a low current density of

72 A/cm2. The broadband spectrum and high

modulation bandwidth are ascribed to the capture of

carriers by different localized states of InGaN QDs with

alleviative QCSE as compared to the traditional

InGaN/GaN quantum well (QW) structures. We

believe the approach reported in this work will find its

potential application in GaN WLEDs and advance the

development of semiconductor lighting-

communication integration.

Tamm plasmons in metal/nanoporous GaN

distributed Bragg reflector cavities for active and

passive optoelectronics Materials Department, University of California Santa

Barbara, Santa Barbara, California 93106, USA

Solid-State Lighting Energy Electronic Center (SSLEEC),

University of California Santa Barbara, Santa Barbara,

California 93106, USA

Department of Physics, University of California Santa

Barbara, Santa Barbara, California 93106, USA

Université Lyon, Université Claude Bernard Lyon 1, CNRS,

Institut Lumière Matière, F-69622 Lyon, France

Optics Express

https://doi.org/10.1364/OE.392546

We theoretically and experimentally investigate

Tamm plasmon (TP) modes in a metal/semiconductor

distributed Bragg reflector (DBR) interface. A thin Ag

(silver) layer with a thickness (55 nm from simulation)

that is optimized to guarantee a low reflectivity at the

resonance was deposited on nanoporous GaN DBRs

fabricated using electrochemical (EC) etching on

freestanding semipolar GaN substrates. The

reflectivity spectra of the DBRs are compared before

and after the Ag deposition and with that of a blanket

Ag layer deposited on GaN. The experimental results

indicate the presence of a TP mode at ∼ 454 nm on

the structure after the Ag deposition, which is also

supported by theoretical calculations using a transfer-

matrix algorithm. The results from mode dispersion

with energy-momentum reflectance spectroscopy

measurements also support the presence of a TP

mode at the metal-nanoporous GaN DBR interface. An

active medium can also be accommodated within the

mode for optoelectronics and photonics. Moreover,

the simulation results predict a sensitivity of the TP

mode wavelength to the ambient (∼ 4-7 nm shift

when changing the ambient within the pores from air

with n = 1 to isopropanol n = 1.3), suggesting an

application of the nanoporous GaN-based TP structure

for optical sensing.

Three-dimensional metal–semiconductor–metal AlN

deep-ultraviolet detector State Key Laboratory of High-Performance Complex


Engineering, Central South University, Changsha, Hunan

410083, China

Key Laboratory of Hunan Province for Efficient Power

System and Intelligent Manufacturing, Shaoyang University,

Shaoyang, Hunan 422000, China

Research and Development Center for Solid State Lighting,



Hunan Key Laboratory of Super-microstructure and

Ultrafast Process, School of Physics and Electronics, Central

South University, Hunan 410083, China

Optics Letters

https://doi.org/10.1364/OL.394338

Conventional metal–semiconductor–metal (MSM)

ultraviolet (UV) detectors have the disadvantage of

limited adjustable structural parameters, finite

electrical field, and long carrier path. In this Letter, we

demonstrate a three-dimensional (3D) MSM structural

AlN-based deep-UV (DUV) detector, fabricated

through simple trench etching and metal deposition,

while flip bonding to the silicon substrate forms a flip-

chip 3D-MSM (FC-3DMSM) device. 3D-MSM devices

exhibit improved responsiveness and response speed,

compared with conventional MSM devices. Time-

dependent photoresponse of all devices is also

investigated here. The enhanced performance of the

3D-MSM device is to be attributed to the intensified

electrical field from the 3D metal electrode

configuration and the inhibition of the carrier vertical

transport, which unambiguously increases the carrier

collection efficiency and migration speed, and thus the

responsivity and speed as well. This work should

advance the design and fabrication of AlN-based DUV

detectors.

https://doi.org/10.1364/OE.392546https://doi.org/10.1364/OL.394338


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560 nm InGaN micro-LEDs on low-defect-density and

scalable (20-21) semipolar GaN on patterned

sapphire substrates Materials Department, University of California Santa

Barbara, Santa Barbara, CA 93117, USA

Department of Electrical and Computer Engineering,

University of California Santa Barbara, CA 93117, USA


University of Yale, CT 06520, USA

Optics Express

https://doi.org/10.1364/OE.387561

We demonstrate InGaN-based semipolar 560 nm

micro-light-emitting diodes with 2.5% EQE on high-

quality and low-defect-density (20-21) GaN templates

grown on scalable and low-cost sapphire substrates.

Through transmission electron microscopy

observations, we discuss how the management of

misfit dislocations and their confinement in areas

away from the active light-emitting region is necessary

for improving device performance. We also discuss

how the patterning of semipolar GaN on sapphire

influences material properties in terms of surface

roughness and undesired faceting in addition to

indium segregation at the proximity of defected areas.

Improving carrier transport in AlGaN deep-ultraviolet

light-emitting diodes using a strip-in-a-barrier

structure Department of Electrical and Computer Engineering, New

Jersey Institute of Technology, 323 Dr. Martin Luther King

Jr. Boulevard, Newark, New Jersey 07102, USA

Institute of Chemical Technology, Vietnam Academy of

Science and Technology, Ho Chi Minh City 700000, Vietnam

Department of Electronics and Communication

Engineering, National Institute of Technology Silchar, Assam

788010, India

Applied Optics

https://doi.org/10.1364/AO.394149

This paper reports the illustration of electron blocking

layer (EBL)-free AlGaN light-emitting diodes (LEDs)

operating in the deep-ultraviolet (DUV) wavelength at

∼270nm. In this work, we demonstrated that the

integration of an optimized thin undoped AlGaN strip

layer in the middle of the last quantum barrier (LQB)

could generate enough conduction band barrier

height for the effectively reduced electron overflow

into the 𝑝-GaN region. Moreover, the hole injection

into the multi-quantum-well active region is

significantly increased due to a large hole

accumulation at the interface of the AlGaN strip and

the LQB. As a result, the internal quantum efficiency

and output power of the proposed LED structure has

been enhanced tremendously compared to that of the

conventional 𝑝-type EBL-based LED structure.

Modelling and optical response of a compressive-

strained AlGaN/GaN quantum well laser diode Laboratory of Metallic and Semiconducting Materials

(LMSM), Department of Electrical Engineering, Biskra

University, Biskra, Algeria

Faculty of Science, Elhadj Lakhdar University, Batnal, Algeria

Research Centre in Industrial Technology (CRTI), Algiers,

Algeria

DIIES – Mediterranea University of Reggio Calabria, Reggio

Calabria, Italy

Journal of Semiconductors

https://doi.org/10.1088/1674-4926/41/6/062301

The effects of the quantum well (QW) width, carrier

density, and aluminium (Al) concentration in the

barrier layers on the optical characteristics of a gallium

nitride (GaN)-based QW laser diode are investigated

by means of a careful modelling analysis in a wide

range of temperatures. The device's optical gain is

calculated by using two different band energy models.

The first is based on the simple band-to-band model

that accounts for carrier transitions between the first

levels of the conduction band and valence band,

whereas the second assumes the perturbation theory

(k.p model) for considering the valence intersubband

transitions and the relative absorption losses in the

QW. The results reveal that the optical gain increases

with increasing the n-type doping density as well as

the Al molar fraction of the AlxGa1–xN layers, which

originate the GaN compressive-strained QW. In

particular, a significant optical gain on the order of

5000 cm–1 is calculated for a QW width of 40 Å at

room temperature. In addition, the laser threshold

current density is of few tens of A/cm2 at low

temperatures.

https://doi.org/10.1364/OE.387561https://doi.org/10.1364/AO.394149https://doi.org/10.1088/1674-4926/41/6/062301


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Size-independent low voltage of InGaN micro-light-

emitting diodes with epitaxial tunnel junctions using

selective area growth by metalorganic chemical

vapor deposition Materials Department, University of California, Santa

Barbara, CA 93106, USA


University of California, Santa Barbara, CA 93106, USA

Optics Express

https://doi.org/10.1364/OE.394664

High performance InGaN micro-size light-emitting

diodes (µLEDs) with epitaxial tunnel junctions (TJs)

were successfully demonstrated using selective area

growth (SAG) by metalorganic chemical vapor

deposition (MOCVD). Patterned n + GaN/n-GaN layers

with small holes were grown on top of standard InGaN

blue LEDs to form TJs using SAG. TJ µLEDs with squared

mesa ranging from 10×10 to 100×100 µm2 were

fabricated. The forward voltage (Vf) in the reference

TJ µLEDs without SAG is very high and decreases

linearly from 4.6 to 3.7 V at 20 A/cm2 with reduction

in area from 10000 to 100 µm2, which is caused by the

lateral out diffusion of hydrogen through sidewall. By

contrast, the Vf at 20 A/cm2 in the TJ µLEDs utilizing

SAG is significantly reduced to be 3.24 to 3.31 V.

Moreover, the Vf in the SAG TJ µLEDs is independent

on sizes, suggesting that the hydrogen is effectively

removed through the holes on top of the p-GaN

surface by SAG. The output power of SAG TJ µLEDs is

∼10% higher than the common µLEDs with indium tin

oxide (ITO) contact.

Enhanced wall plug efficiency of AlGaN-based deep-

UV LEDs using Mo/Al as p-contact Ferdinand-Braun-Institut, Leibniz-Institut für

Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489

Berlin, Germany

Institute of Solid State Physics, Hardenbergstr. 36, EW 6-1,

10623 Berlin, Germany

IEEE Photonics Technology Letters

https://doi.org/10.1109/LPT.2020.3003164

P-type contacts with a high reflectivity in the

ultraviolet spectral region made of

molybdenum/aluminum (Mo/Al) on AlGaN-based

deep-ultraviolet light-emitting diodes (DUV LEDs)

emitting at 265 nm have been investigated. Optimized

Mo/Al contacts are shown to have a high optical

reflectivity above 75 % at 265 nm. DUV LEDs with an

absorbing p-AlGaN heterostructure operated at 20 mA

show a 15 % higher light output power and a 1 V lower

voltage when Mo/Al instead of Pt is used as p-contact.

The effect on the voltage of DUV LEDs with a UV-

transparent p-side heterostructure is similar.

Moreover, DUV LEDs with a Mo/Al contact show a

lower operation voltage compared to LEDs with an

indium tin oxide/aluminum (ITO/Al) p-contact where

the ITO is intended to form a semitransparent low-

resistance contact and the Al serves as a reflector.

Implementation of the inductively coupled plasma

etching processes for forming gallium nitride

nanorods used in ultraviolet light-emitting diode

technology Łukasiewicz Research Network-Institute of Electron

Technology, Al.Lotników 32/46, 02-668 Warsaw, Poland

Institute of Physics, Silesian University of Technology, ul.

Konarskiego 22B, 44-100 Gliwice, Poland

Warsaw University of Technology, Institute of

Microelectronics and Optoelectronics, ul. Koszykowa 75,

00-662 Warsaw, Poland

Journal of Vacuum Science & Technology B

https://doi.org/10.1116/6.0000133

This report presents the results of fabricating GaN

nanorods by inductively coupled plasma etching using

BCl3/Cl2 chemistry. Interestingly, the GaN nanorods

are formed only in the area initially masked by the

sacrificial metal mask. In addition to the metallic mask,

a specific feature of this process is the application of

an insulating ceramic carrier for the improvement of

the process performance. The authors show that using

the same etching parameters but with a conductive

silicon carrier significantly reduces the efficiency of

nanorod formation. Auger electron spectroscopy was

applied to propose and confirm the mechanism of

nanorod formation ceramic carrier and properly

selected metallic masks. The usefulness of the

developed method of nanorod production has been

confirmed by its application in the fabrication and

characterization of GaN-based UV light-emitting

diodes.

https://doi.org/10.1364/OE.394664https://doi.org/10.1109/LPT.2020.3003164https://doi.org/10.1116/6.0000133


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Impact of defects on Auger recombination in c-plane

InGaN/GaN single quantum well in the efficiency

droop regime Institute of Physics, École Polytechnique Fédérale de

Lausanne (EPFL), CH-1015 Lausanne, Switzerland

Applied Physics Letters

https://doi.org/10.1063/5.0004321

We study the impact of non-radiative defects on Auger

recombination in c-plane InGaN/GaN single quantum

wells (SQWs) in the efficiency droop regime using high

injection time-resolved photoluminescence. The

defect density in the SQW is controlled by tuning the

thickness of an InAlN underlayer. When the defect

density is increased, apart from Shockley–Read–Hall

(SRH) and standard Auger recombination, introducing

an extra defect-assisted Auger process is required to

reconcile the discrepancy observed between the usual

ABC model and experimental data. We derive a linear

dependence between the SRH coefficient and the

bimolecular defect-assisted Auger coefficient, which

suggests that the generated defects can act as

scattering centers responsible for indirect Auger

processes. In particular, in defective SQWs, the defect-

assisted Auger recombination rate can exceed the

radiative one. Our results further suggest that the

defect-assisted Auger recombination is expected to be

all the more critical in green to red III-nitride light-

emitting diodes due to their reduced radiative rate.

Thermal droop in III-nitride based light-emitting

diodes: Physical origin and perspectives Department of Information Engineering, University of

Padova, via Gradenigo 6/b, 35131 Padova, Italy

Department of Electronics and Telecommunications,

Politecnico di Torino, corso Duca degli Abruzzi 24, 10129

Turin, Italy

Consiglio Nazionale delle Ricerche (CNR), Istituto di

Elettronica e di Ingegneria dell'Informazione e delle

Telecomunicazioni (IEIIT), corso Duca degli Abruzzi 24,

10129 Turin, Italy

Journal of Applied Physics

https://doi.org/10.1063/5.0005874

This tutorial paper focuses on the physical origin of

thermal droop, i.e., the decrease in the luminescence

of light-emitting diodes (LEDs) induced by increasing

temperature. III-nitride-based LEDs are becoming a

pervasive technology, covering several fields from

lighting to displays, from automotive to portable

electronics, and from horticulture to sensing. In all

these environments, high efficiency is a fundamental

requirement, for reducing power consumption and

system cost. Over the last decade, a great deal of

effort has been put in the analysis of the efficiency

droop, the decrease in LED internal quantum

efficiency (IQE) induced by high current density. On

the other hand, an IQE decrease is observed also for

increasing temperature, a phenomenon usually

referred to as thermal droop. For commercial LEDs,

the IQE decrease related to thermal droop can be

comparable to that of efficiency droop: for this reason,

understanding thermal droop is a fundamental step

for making LEDs capable of operating at high

temperature levels. In several fields (including street

lighting, automotive, photochemical treatments,

projection, entertainment lighting, etc.), compact and

high-flux light sources are required: typically, to

reduce the size, weight, and cost of the systems, LEDs

are mounted in compact arrays, and heat sinks are

reduced to a minimum. As a consequence, LEDs can

easily reach junction temperatures above 85–100 °C

and are rated for junction temperatures up to 150–

175 °C (figures from commercially available LED

datasheets: Cree XHP70, Osram LUW HWQP, Nichia

NVSL219CT, Samsung LH351B, and LedEngin LZP-

00CW0R) and this motivates a careful analysis of

thermal droop. This paper discusses the possible

physical causes of thermal droop. After an

introduction on the loss mechanisms in junctions, we

will individually focus on the following processes: (i)

Shockley–Read–Hall (SRH) recombination and

properties of the related defects; (ii) Auger

recombination and its temperature dependence,

including the discussion of trap-assisted Auger

recombination; (iii) impact of carrier transport on the

thermal droop, including a discussion on carrier

delocalization, escape, and freeze out; (iv) non-SRH

defect-related droop mechanisms. In addition, (v) we

discuss the processes that contribute to light emission

at extremely low current levels and (vi) the thermal

droop in deep ultraviolet LEDs, also with reference to

the main parasitic emission bands. The results

presented within this paper give a tutorial perspective

on thermal droop; in addition, they suggest a pathway

for the mitigation of this process and for the

https://doi.org/10.1063/5.0004321https://doi.org/10.1063/5.0005874


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development of LEDs with stable optical output over a

broad temperature range.

Lasing up to 380 K in a sublimated GaN nanowire Nanophotonics Center, NTT Corp., 3-1, Morinosato

Wakamiya Atsugi, Kanagawa 243-0198, Japan

NTT Basic Research Laboratories, NTT Corp., 3-1,

Morinosato Wakamiya Atsugi, Kanagawa 243-0198, Japan

Université Côte d'Azur, CNRS, CRHEA, Rue B. Grégory,

06560 Valbonne, France

NTT Device Technology Laboratory, NTT Corp., 3-1,

Morinosato Wakamiya Atsugi, Kanagawa 243-0198, Japan


https://doi.org/10.1063/5.0004771

We report on GaN nanowire lasers fabricated by

selective-area sublimation, and we show that

sublimated GaN nanowires can exhibit ultraviolet

lasing action under optical pumping beyond room

temperature, up to 380 K. We study by

microphotoluminescence the temperature-

dependent behavior of single nanowire lasers

between 7 K and 380 K and extract a characteristic

temperature of T = 126 K. We finally present a

statistical study of the maximum lasing temperature in

individual sublimated GaN nanowires and use it to

assess the performance of the selective-area

sublimation method for nanowire-based lasing

applications.

Au-Nanoplasmonics-Mediated Surface Plasmon-

Enhanced GaN Nanostructured UV Photodetectors Department of Electronics and Communication

Engineering, Delhi Technological University, New Delhi

110042, India

CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road,

New Delhi 110012, India

Academy of Scientific and Innovative Research, CSIR-HRDC

Campus, Ghaziabad, Uttar Pradesh 201002, India

ACS Omega

https://doi.org/10.1021/acsomega.0c01239

The nanoplasmonic impact of chemically synthesized

Au nanoparticles (Au NPs) on the performance of GaN

nanostructure-based ultraviolet (UV) photodetectors

is analyzed. The devices with uniformly distributed Au

NPs on GaN nanostructures (nanoislands and

nanoflowers) prominently respond toward UV

illumination (325 nm) in both self-powered as well as

photoconductive modes of operation and have shown

fast and stable time-correlated response with

significant enhancement in the performance

parameters. A comprehensive analysis of the device

design, laser power, and bias-dependent responsivity

and response time is presented. The fabricated Au

NP/GaN nanoflower-based device yields the highest

photoresponsivity of ∼ 380 mA/W, detectivity of ∼

1010 jones, reduced noise equivalent power of ∼ 5.5

× 10–13 W Hz–1/2, quantum efficiency of ∼ 145%, and

fast response/recovery time of ∼40 ms. The report

illustrates the mechanism where light interacts with

the chemically synthesized nanoparticles guided by

the surface plasmon to effectively enhance the device

performance. It is observed that the Au NP-stimulated

local surface plasmon resonance effect and reduced

channel resistance contribute to the augmented

performance of the devices. Further, the decoration of

low-dimensional Au NPs on GaN nanostructures acts

as a detection enhancer with a fast recovery time and

paves the way toward the realization of energy-

efficient optoelectronic device applications.

Demonstration of efficient semipolar 410 nm violet

laser diodes heteroepitaxially grown on high-quality

low-cost GaN/sapphire substrates Materials Department, University of California, Santa

Barbara, CA 93106, USA


University of California, Santa Barbara, CA 93106, USA

ACS Appl. Electron. Mater.

https://doi.org/10.1021/acsaelm.0c00364

Heteroepitaxial growth of semipolar laser diodes (LDs)

on foreign substrate is extremely challenging but

crucial to reduce the cost of semipolar bulk GaN

substrates. In this work, we demonstrate the first

efficient semipolar 410 nm violet LDs grown on high-

quality low-cost semipolar GaN/sapphire substrates.

The fabricated semipolar LD exhibits a high output

power of more than 900 mW at 1.6 A, and a wall-plug

efficiency of 5.6% under pulsed operation. The

analysis also quantitatively confirms that the high

density of defects and high non-radiative

recombination rate in the active region account for the

high transparency current observed in the devices.

https://doi.org/10.1063/5.0004771https://doi.org/10.1021/acsomega.0c01239https://doi.org/10.1021/acsaelm.0c00364


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RGB arrays for micro-LED applications using

nanoporous GaN embedded with quantum dots Department of Electrical Engineering, Yale University, New

Haven 06520, United States

Department of Chemical and Environmental Engineering,

Yale University, New Haven 06520, United States

Energy Sciences Institute, Yale University, West Haven

06516, United States

Department of Physics, Chonnam National University,

Gwangju 61186, Republic of Korea

Electronic and Optoelectronic System Research

Laboratories, Industrial Technology Research Institute ITRI,

Hsinchu, Taiwan

ACS Appl. Mater. Interfaces

https://doi.org/10.1021/acsami.0c00839

The multiple light scattering of nanoporous (NP) GaN

was systematically studied and applied to the color

down-conversion for micro-LED display applications.

The transport mean free path (TMFP) in NP GaN is 660

nm at 450 nm (light wavelength) and it decreases with

decreasing wavelength. It was observed that the short

TMFP of the NP GaN increased the light extinction

coefficient at 370 nm by 11 times. Colloidal QDs were

loaded into half 4” wafer-scale NP GaN, and 96 and

100% light conversion efficiencies for green and red

were achieved, respectively. By loading green and red

QDs selectively into NP GaN mesas, we demonstrated

the RGB micro-arrays based on the blue-violet

pumping light with green and red color converting

regions.

Reversing abnormal hole localization in high-Al-

content AlGaN quantum well to enhance deep

ultraviolet emission by regulating the orbital state

coupling Engineering Research Center of Micro-nano Optoelectronic

Materials and Devices, Ministry of Education; Fujian

Provincial Key Laboratory of Semiconductor Materials and

Applications; Collaborative Innovation Center for

Optoelectronic Semiconductors and Efficient Devices;

Department of Physics, Xiamen University, 361005 Xiamen,

China

Light: Science & Applications

https://doi.org/10.1038/s41377-020-00342-3

AlGaN has attracted considerable interest for

ultraviolet (UV) applications. With the development of

UV optoelectronic devices, abnormal carrier

confinement behaviour has been observed for c-

plane-oriented AlGaN quantum wells (QWs) with high

Al content. Because of the dispersive crystal field split-

off hole band (CH band) composed of pz orbitals, the

abnormal confinement becomes the limiting factor for

efficient UV light emission. This observation differs

from the widely accepted concept that confinement of

carriers at the lowest quantum level is more

pronounced than that at higher quantum levels, which

has been an established conclusion for conventional

continuous potential wells. In particular, orientational

pz orbitals are sensitive to the confinement direction

in line with the conducting direction, which affects the

orbital intercoupling. In this work, models of

Al0.75Ga0.25N/AlN QWs constructed with variable

lattice orientations were used to investigate the

orbital intercoupling among atoms between the well

and barrier regions. Orbital engineering of QWs was

implemented by changing the orbital state

confinement, with the well plane inclined from 0° to

90° at a step of 30° (referred to the c plane). The

barrier potential and transition rate at the band edge

were enhanced through this orbital engineering. The

concept of orbital engineering was also demonstrated

through the construction of inclined QW planes on

semi- and nonpolar planes implemented in microrods

with pyramid-shaped tops. The higher emission

intensity from the QWs on the nonpolar plane

compared with those on the polar plane was

confirmed via localized cathodoluminescence (CL)

maps.

Mini-LED, Micro-LED and OLED displays: present

status and future perspectives College of Optics and Photonics, University of Central

Florida, Orlando, FL, 32816, USA

Light: Science & Applications

https://doi.org/10.1038/s41377-020-0341-9

Presently, liquid crystal displays (LCDs) and organic

light-emitting diode (OLED) displays are two dominant

flat panel display technologies. Recently, inorganic

mini-LEDs (mLEDs) and micro-LEDs (μLEDs) have

emerged by significantly enhancing the dynamic range

of LCDs or as sunlight readable emissive displays.

“mLED, OLED, or μLED: who wins?” is a heated

debatable question. In this review, we conduct a

https://doi.org/10.1021/acsami.0c00839https://doi.org/10.1038/s41377-020-00342-3https://doi.org/10.1038/s41377-020-0341-9


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comprehensive analysis on the material properties,

device structures, and performance of

mLED/μLED/OLED emissive displays and mLED backlit

LCDs. We evaluate the power consumption and

ambient contrast ratio of each display in depth and

systematically compare the motion picture response

time, dynamic range, and adaptability to

flexible/transparent displays. The pros and cons of

mLED, OLED, and μLED displays are analysed, and their

future perspectives are discussed.

External Quantum Efficiency of 6.5% at 300nm

emission and 4.7% at 310nm emission on bare-wafer

of AlGaN-based UVB LEDs RIKEN Cluster for Pioneering Research (CPR), 2-1 Hirosawa,

Wako, Saitama 351-0198, Japan

RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa,

Wako, Saitama 351-0198, Japan

Yamaguchi University, 2-16-1 Tokiwadai, Ube Yamaguchi

755-8611, Japan

ACS Appl. Electron. Mater.

https://doi.org/10.1021/acsaelm.0c00172

By the Minamata Convention on Mercury, regulation

on Mercury use will be stricter from this year of 2020

and safe AlGaN-based ultraviolet (UV) light sources are

urgently needed for killing of SARS-CoV-2 (corona

virus). AlGaN-based ultraviolet‐B (UVB) light‐emitting

diodes (LEDs) and UVB laser diodes (LDs) have the

potential to replace toxic mercury UV-Lamps.

Previously, the internal-quantum-efficiency (ηint)

were enhanced from 47% to 54% in AlGaN UVB multi-

quantum-well (MQWs). However, some non-linear

behavior in both light output power (L) and external-

quantum-efficiency (ηext) in the 310nm-band UVB

LEDs were observed and later on such nonlinearities

were overcome by reducing the thicknesses of

quantum-well-barriers (TQWB) in MQWs. After

relaxing to the n-AlGaN electron injection layer (EIL)

up to 50% underneath the MQWs and using highly

reflective Ni/Al p-electrode, the L and ηext,

respectively, of 310nm-band UVB LED were greatly

improved from 12 mW and 2.3% to a record value of

29 mW and 4.7%. Similarly, for 294nm-band UVB LED,

the ηext and L, respectively, were also remarkably

improved up to 6.5% and 32 mW at RT on bare-wafer

condition, using better carrier confinement scheme in

the MQWs as well as using moderately Mg-doped p-

type multi-quantum-barrier electron-blocking-layer

(p-MQB EBL). Moderately doped p-MQB EBL was

aimed for better hole transport to enhance the hole

injection toward the MQWs as well as to block the high

energy electron from overshooting. Possible

explanations and recommendations for the

improvements in the performances of 294-310nm

UVB LEDs are broadly discussed. Most importantly,

such controllable multi UVB-wavelength emitters may

extend nitride‐based LEDs to previously inaccessible

areas, for example, electrically pumped AlGaN-based

UVB LDs.

Unidirectional luminescence from InGaN/GaN

quantum-well metasurfaces Department of Electrical and Computer Engineering,

University of California Santa Barbara, Santa Barbara, CA,

USA

Department of Physics, University of California Santa

Barbara, Santa Barbara, CA, USA

Department of Material Science and Engineering, University

of California Santa Barbara, Santa Barbara, CA, USA

Solid State Lighting and Energy Electronics Center,

University of California Santa Barbara, Santa Barbara, CA,

USA

Nature Photonics

https://doi.org/10.1038/s41566-020-0641-x

III–nitride light-emitting diodes (LEDs) are the

backbone of ubiquitous lighting and display

applications. Imparting directional emission is an

essential requirement for many LED implementations.

Although optical packaging1, nanopatterning2,3 and

surface roughening4 techniques can enhance LED

extraction, directing the emitted light requires bulky

optical components. Optical metasurfaces provide

precise control over transmitted and reflected

waveforms, suggesting a new route for directing light

emission. However, it is difficult to adapt metasurface

concepts for incoherent light emission, due to the lack

of a phase-locking incident wave. Here, we

demonstrate a metasurface-based design of

InGaN/GaN quantum-well structures that generate

narrow, unidirectional transmission and emission

lobes at arbitrary engineered angles. We further

demonstrate 7-fold and 100-fold enhancements of

total and air-coupled external quantum efficiencies,

respectively. The results present a new strategy for

https://doi.org/10.1021/acsaelm.0c00172https://doi.org/10.1038/s41566-020-0641-x


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exploiting metasurface functionality in light-emitting

devices.

Quasi‐2D Growth of Aluminum Nitride Film on

Graphene for Boosting Deep Ultraviolet Light‐

Emitting Diodes Research and Development Center for Semiconductor

Lighting Technology, Institute of Semiconductors, Chinese

Academy of Sciences, Beijing, 100083 China

Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,

Beijing, 100049 China

Beijing Graphene Institute (BGI), Beijing, 100095 China

Center for Nanochemistry (CNC), Beijing Science and

Engineering Center for Nanocarbons, College of Chemistry

and Molecular Engineering, Peking University, Beijing,

100871 China

Electron Microscopy Laboratory, and International Center

for Quantum Materials, School of Physics, Peking University,


State Key Laboratory of Superlattices and Microstructures,



Center of Materials Science and Optoelectronics

Engineering, University of Chinese Academy of Sciences,


School of Electronics and Information Engineering, Hebei

University of Technology, Tianjin, 300401 China

Research and Development Center for Semiconductor

Lighting Technology, Institute of Semiconductors, Chinese

Academy of Sciences, Beijing, 100083 China

Collaborative Innovation Center of Quantum Matter,


Advanced Science

https://doi.org/10.1002/advs.202001272

Efficient and low‐cost production of high‐quality

aluminum nitride (AlN) films during heteroepitaxy is

the key for the development of deep ultraviolet light‐

emitting diodes (DUV‐LEDs). Here, the quasi‐2D

growth of high‐quality AlN film with low strain and low

dislocation density on graphene (Gr) is presented and

a high‐performance 272 nm DUV‐LED is

demonstrated. Guided by first‐principles calculations,

it is found that AlN grown on Gr prefers lateral growth

both energetically and kinetically, thereby resulting in

a Gr‐driven quasi‐2D growth mode. The strong lateral

growth mode enables most of dislocations to

annihilate each other at the AlN/Gr interface, and

therefore the AlN epilayer can quickly coalesce and

flatten the nanopatterned sapphire substrate. Based

on the high quality and low strain of AlN film grown on

Gr, the as‐fabricated 272 nm DUV‐LED shows a 22%

enhancement of output power than that with low‐

temperature AlN buffer, following a negligible

wavelength shift under high current. This facile

strategy opens a pathway to drastically improve the

performance of DUV‐LEDs.

Dislocation‐Free and Atomically Flat GaN Hexagonal

Microprisms for Device Applications Solid State Physics and NanoLund, Lund University, Box 118,

Lund, 221 00 Sweden

nCHREM/Centre for Analysis and Synthesis and NanoLund,

Lund University, Box 124, Lund, 221 00 Sweden

Synchrotron Radiation Research and NanoLund, Lund

University, Box 118, Lund, 221 00 Sweden

small

https://doi.org/10.1002/smll.201907364

III‐nitrides are considered the material of choice for

light‐emitting diodes (LEDs) and lasers in the visible to

ultraviolet spectral range. The development is

hampered by lattice and thermal mismatch between

the nitride layers and the growth substrate leading to

high dislocation densities. In order to overcome the

issue, efforts have gone into selected area growth of

nanowires (NWs), using their small footprint in the

substrate to grow virtually dislocation‐free material.

Their geometry is defined by six tall side‐facets and a

pointed tip which limits the design of optoelectronic

devices. Growth of dislocation‐free and atomically

smooth 3D hexagonal GaN micro‐prisms with a flat,

micrometer‐sized top‐surface is presented. These self‐

forming structures are suitable for optical devices such

as low‐loss optical cavities for high‐efficiency LEDs.

The structures are made by annealing GaN NWs with

a thick radial shell, reforming them into hexagonal flat‐

top prisms with six equivalents either m‐ or s‐facets

depending on the initial heights of the top pyramid

and m‐facets of the NWs. This shape is kinetically

controlled and the reformation can be explained with

a phenomenological model based on Wulff

construction that have been developed. It is expected

that the results will inspire further research into

micron‐sized III‐nitride‐based devices.

https://doi.org/10.1002/advs.202001272https://doi.org/10.1002/smll.201907364


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Fabrication and applications of wafer-scale

nanoporous GaN near-infrared distributed Bragg

reflectors School of Microelectronics, Shandong University, Jinan,

250100, PR China

School of Physics, Shandong University, Jinan, 250100, PR

China

Optical Materials

https://doi.org/10.1016/j.optmat.2020.110093

The wafer-scale, near-infrared, and nanoporous (NP)-

GaN distributed Bragg reflectors (DBRs) were

fabricated by using an electrochemical anodization

method for the first time. The peak reflectivity of the

DBR mirrors on the sapphire substrates is ~95% in the

range of 550 nm–1750 nm with different stop-band

widths. To explore its potential applications, a lead-

free all-inorganic perovskite film with a PL emission in

the near-infrared region was grown on a DBR mirror.

Compared to the reference perovskite film, the

photoluminescence intensity of the perovskite film on

the DBR substrate presents more than 4-fold

enhancement, which is in agreement with the

calculated value. The performance enhancement

should be contributable to light-coupling

enhancement of emission light. The near-infrared NP-

GaN DBRs pave the way for developing a range of

perovskite devices for broadband and large-area

applications.

Ultrawide bandgap AlN metasurfaces for ultraviolet

focusing and routing State Key Laboratory of High Performance Complex


Engineering, Central South University, Changsha, Hunan

410083, China

State Key Laboratory of Advanced Design and

Manufacturing for Vehicle Body, College of Mechanical and

Vehicle Engineering, Hunan University, Changsha 410082,

China

Research and Development Center for Solid State Lighting,



Optics Letters

https://doi.org/10.1364/OL.395909

All-dielectric metasurfaces offer a promising way to

control amplitude, polarization, and phase of light.

However, ultraviolet (UV) component metasurfaces

are rarely reported due to significant absorption loss

for most dielectric materials and the required smaller

footprint or feature size. Here, we demonstrate

broadband UV focusing and routing in both

transmission and reflection modes in simulations by

adopting aluminum nitride (AlN) with ultrawide

bandgap and a waveplate metasurface structure. As

for experiments, the on-axis, off-axis focusing

characteristics in transmission mode have been

investigated at representative UVA (375 nm)

wavelength for the first time, to the best of our

knowledge. Furthermore, we fabricated a UV

transmission router for monowavelength, guiding UV

light to the designated different spatial positions of

the same or different focal planes. Our work is

meaningful for the development of UV photonics

components and devices and would facilitate the

integration and miniaturization of UV nanophotonics.

Revealing the importance of light extraction

efficiency in InGaN/GaN microLEDs via chemical

treatment and dielectric passivation editors-pick Department of Chemical Engineering, University of

California, Santa Barbara, California 93106, USA

Materials Department, University of California, Santa

Barbara, California 93106, USA


University of California, Santa Barbara, California 93106,

USA


https://doi.org/10.1063/5.0011651

Chemical etching and Al2O3 dielectric passivation

were used to minimize nonradiative sidewall defects

in InGaN/GaN microLEDs (mesa diameter = 2–

100 μm), resulting in an increase in external quantum

efficiency (EQE) as the LED size was decreased. Peak

EQEs increased from 8%–10% to 12%–13.5% for mesa

diameters from 100 μm to 2 μm, respectively, and no

measurable leakage currents were seen in current

density–voltage (J–V) characteristics. The position and

shape of EQE curves for all devices were essentially

identical, indicating size-independent ABC model

(Shockley–Read–Hall, radiative, and Auger

recombination) coefficients-behavior that is not

typical of microLEDs as the size decreases. These

trends can be explained by enhancement in light

https://doi.org/10.1016/j.optmat.2020.110093https://doi.org/10.1364/OL.395909https://doi.org/10.1063/5.0011651


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extraction efficiency (LEE), which is only observable

when sidewall defects are minimized, for the smallest

LED sizes. Detailed ray-tracing simulations

substantiate the LEE enhancements.

Enhancing carrier transport and carrier capture with

a good current spreading characteristic via graphene

transparent conductive electrodes in InGaN/GaN

multiple-quantum-well light emitting diodes Department of Applied Physics, National University of

Kaohsiung No. 700, Kaohsiung University Road, Nan-Tzu

Dist., 811, Kaohsiung City, Taiwan (R.O.C.)

LiveStrong Optoelectronics Cooperation, No. 82, Luke 5th

Rd., Kaohsiung City, 821, Taiwan (R.O.C.)

Department of Mechanical Engineering and Advanced

Institute of Manufacturing with High-tech Innovations,

National Chung Cheng University, No. 168, Sec. 1, University

Rd., Chia-yi, 621301, Taiwan (R.O.C.)

Scientific Reports

https://doi.org/10.1038/s41598-020-67274-1

In this work, InGaN/GaN multiple-quantum-wells

light-emitting diodes with and without graphene

transparent conductive electrodes are studied with

current-voltage, electroluminescence, and time-

resolved electroluminescence (TREL) measurements.

The results demonstrate that the applications of

graphene electrodes on LED devices will spread

injection carriers more uniformly into the active region

and therefore result in a larger current density,

broader luminescence area, and stronger EL intensity.

In addition, the TREL data will be further analyzed by

employing a 2-N theoretical model of carrier

transport, capture, and escape processes. The

combined experimental and theoretical results clearly

indicate that those LEDs with graphene transparent

conductive electrodes at p-junctions will have a

shorter hole transport time along the lateral direction

and thus a more efficient current spreading and a

larger luminescence area. In addition, a shorter hole

transport time will also expedite hole capture

processes and result in a shorter capture time and

better light emitting efficiency. Furthermore, as more

carrier injected into the active regions of LEDs, thanks

to graphene transparent conductive electrodes,

excessive carriers need more time to proceed carrier

recombination processes in QWs and result in a longer

carrier recombination time. In short, the LED samples,

with the help of graphene electrodes, are shown to

have a better carrier transport efficiency, better

carrier capture efficiency, and more electron-hole

recombination. These research results provide

important information for the carrier transport,

carrier capture, and recombination processes in

InGaN/GaN MQW LEDs with graphene transparent

conductive electrodes.

Flexible perylenediimide/GaN organic–inorganic

hybrid system with exciting optical and interfacial

properties Photovoltaic Metrology Group, CSIR-National Physical

Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012,

India

2D Physics and QHR Metrology Group, CSIR-National

Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi,

110012, India

Photonics Materials Metrology Group, CSIR-National

Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi,

110012, India

Thin Film Gas Metrology Group, CSIR-National Physical

Laboratory, Dr. K. S. Krishnan Marg, New Delhi, 110012,

India

Department of Electronics and Communication

Engineering, Indian Institute of Information Technology

Allahabad, Prayagraj, 211015, India

Spintronics and Magnetic Materials Laboratory,

Department of Applied Sciences, Indian Institute of

Information Technology Allahabad, Prayagraj, 211015, India

Scientific Reports

https://doi.org/10.1038/s41598-020-67531-3

We report the band gap tuning and facilitated charge

transport at perylenediimide (PDI)/GaN interface in

organic–inorganic hybrid nanostructure system over

flexible titanium (Ti) foil. Energy levels of the materials

perfectly align and facilitate high efficiency charge

transfer from electron rich n-GaN to electron deficient

PDI molecules. Proper interface formation resulted in

band gap tuning as well as facilitated electron

transport as evident in I–V characteristics. Growth of

PDI/GaN hybrid system with band gap tuning from

ultra-violet to visible region and excellent electrical

properties open up new paradigm for fabrication of

efficient optoelectronics devices on flexible

substrates.

https://doi.org/10.1038/s41598-020-67274-1https://doi.org/10.1038/s41598-020-67531-3


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GaN/AlN Multiple Quantum Wells grown by

Molecular Beam Epitaxy: Effect of growth kinetics on

radiative recombination efficiency Centre for Research in Nanoscience and Nanotechnology,

University of Calcutta, JD2 Sector III Salt Lake City, Kolkata-

700106, West Bengal, India

Institute of Radio Physics and Electronics, University of

Calcutta, 92 A. P. C. Road, Kolkata-700009, West Bengal,

India

School of Biological Sciences, Indian Association for the

Cultivation of Science, Kolkata 700032, India

Thin Solid Films

https://doi.org/10.1016/j.tsf.2020.138216

Ultraviolet (UV) optoelectronic devices based on

binary GaN quantum wells have been widely reported

in the literature. The internal quantum efficiency (IQE)

of such structures is relatively low due to the large

dislocation densities generated during heteroepitaxial

deposition on to non lattice-matched substrates.

Enhancement of IQE is possible through the use of

expensive lattice-matched substrates or by using

complex dislocation density reducing mechanisms. In

this paper we have investigated growth mechanisms

of GaN/AlN multiple quantum wells (MQWs) using

Plasma Assisted Molecular Beam Epitaxy. Specifically

the modulation of the surface diffusivity of adatoms

has been carried out through choice of appropriate

growth parameters, such as the group-III to group-V

flux ratio. Our results indicate that this leads to

modification of not only the surface morphology, but

also the abruptness of the well-barrier interface.

Under conditions of growth where surface

morphology was atomically flat, the interfaces are

relatively diffuse. The IQE for such structures, as

measured by the ratio of room temperature

photoluminescence intensity to that measured at 4 K,

is rather low typically ∼10%. Use of near

stoichiometric growth conditions however lead to a

reduction of the surface diffusivity of adatoms, and

the formation of spontaneous nanostructures in the

form of nano-dots of about 20 nm in diameter and

high levels of uniformity. The IQE for GaN/AlN MQWs

grown under such conditions is increased to as high as

28% even for samples with large dislocation densities.

Thus, growth under such conditions can mitigate the

detrimental effects of non-radiative recombination

centers associated with dislocations by spatial

localization of electron-hole pairs. These results are

important to many applications, including UV light

emitting diodes.

Enhancement of the optoelectronic characteristics of

deep ultraviolet nanowire laser diodes by induction

of bulk polarization charge with graded AlN

composition in AlxGa1-xN waveguide National Center for International Joint Research of

Electronic Materials and Systems, Zhengzhou University,

Zhengzhou, Henan, China

International Joint-Laboratory of Electronic Materials and

Systems of Henan Province, Zhengzhou University,


Department of Electronics and Information Engineering,

School of Information Engineering, Zhengzhou University,


Zhengzhou Way Electronic Co. Ltd, Zhengzhou, Henan,

China

Superlattices and Microstructures

https://doi.org/10.1016/j.spmi.2020.106643

AlGaN based Nanowire laser diodes (NW-LDs) grown

on sapphire substrates have strong polarization

induced electric field. Such electric field has the ability

to degrade the optoelectronic characteristics of deep

ultraviolet (DUV) NW-LD. In this work, a graded AlN

composition AlxGa1-xN waveguide (WG) layer is used

for the enhancement of DUV NW-LD performance.

Grading of WG induces bulk polarization charges

which compensates the effect of polarization induced

electric field. According to the calculated

optoelectronic characteristics of NW-LD, it is found

that grading of n-type WG (n-WG) increases the

optical confinement factor (OCF) by 82%. Fortunately,

the proposed graded n-WG structure suppresses the

leakage of optical field from active region and

enhances carrier injection efficiency. Furthermore, if

both n-WG and p-WG graded layers are used, the

improvement is not obvious because of the current

leakage from graded p-WG. Thus, graded n-WG based

NW-LD gives highest 33.5% OCF with the lowest  mA

and 4.59 V threshold current and voltage respectively.

https://doi.org/10.1016/j.tsf.2020.138216https://doi.org/10.1016/j.spmi.2020.106643


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High nitrogen flux plasma-assisted molecular bean

epitaxy growth of InxGa1-xN films Materials Department, University of California, Santa

Barbara, CA 93106, United States

Journal of Crystal Growth

https://doi.org/10.1016/j.jcrysgro.2020.125738

Growth of efficient III-N based light emitting devices

by plasma assisted molecular beam epitaxy has been

elusive, even though the technique has attractive

advantages in comparison to metal organic chemical

vapor deposition. Modern high-flux radio frequency

plasma systems could remedy this issue by enabling

growth of InxGa1-xN at higher temperatures than

previously possible, likely improving the material

quality. In this work, active nitrogen fluxes of up to 3.5

μm/h GaN-equivalent growth rate were employed to

grow InxGa1-xN alloys. InxGa1-xN growth rates of 1.3

μm/h were demonstrated at growth temperatures of

550 °C and 600 °C with maximum film compositions of

In0.25Ga0.75N and In0.21Ga0.79N, respectively. A

composition of In0.05Ga0.95N was observed in a film

grown at 700 °C with smooth step-terrace

morphology.

The influence of point defects on AlGaN-based deep

ultraviolet LEDs State Key Laboratory of Integrated Optoelectronics,


No. A35, Qinghua East Road, Haidian District, Beijing,

100083, China

Center of Materials Science and Optoelectronic

Engineering, University of Chinese Academy of Sciences, No.

19A, Yuquan Road, Shijingshan District, Beijing, 100049,

China

School of Physics and Astronomy, University of Nottingham,

Nottingham NG7 2RD, UK

Shanghai Key Laboratory of Multidimensional Information

Processing, School of Communication and Electronic

Engineering, East China Normal University, Shanghai, China

Physics Department, Faculty of Science, Princess Nourah

Bint Abdulrahman University, Riyadh, Saudi Arabia

Journal of Alloys and Compounds

https://doi.org/10.1016/j.jallcom.2020.156177

AlGaN-based deep ultraviolet LEDs with high Al

composition are promising for many applications,

including air- or water-purification, fluorescence

sensing, etc. However, to realize their full potential, it

is important to understand the impact of the point

defects on the device performance. Here, we

investigate the defects in the 26 nm AlGaN-based

deep ultraviolet LEDs after degradation systematically

with a combination of different analytical

technologies. The results show that point defects

increase after the degradation. The generated defects

during the stress lead to a carrier redistribution in the

active region and the induced point defects during the

degradation are located within the multi-quantum

wells (MQWs) region, especially in the first quantum

well near the p side of the LED chip. The dislocation

lines in the MQWs region were also observed after the

degradation, which can lead to the Mg diffusion along

the dislocation line. These findings are important to

understand the defects in AlGaN quantum wells and

further improve AlGaN-based deep ultraviolet LEDs

performance.

Improved contact properties of single-walled carbon

nanotube on p-AlGaN layers after microwave post-

treatment Department of Electrical Engineering, Sejong University,

Seoul, 05006, South Korea

Department of Electrical Engineering and Computer

Science, University of Michigan, Ann Arbor, MI, 48109,

United States

Materials Chemistry and Physics

https://doi.org/10.1016/j.matchemphys.2020.123471

We present improved contact and transparent

properties of single-walled carbon nanotube (SWNT)

transparent conductive electrodes (TCEs) on the p-

AlGaN layer via a post microwave treatment (MWT)

method. As a result, the contact resistance of the

MWT-SWNT TCEs was observed to be 9.7 × 10-2

Ω∙cm2, which was 26.5% lower than that of pristine

sample, while the transmittance is improved by 1.6%

(at the wavelengths of 365 nm) after the MWT. In

addition, the results of material and chemical analyses

show that these improvements might contribute to

the reduction in the Schottky barrier height between

the TCE and the p-AlGaN layer, through both a

generation of Ga vacancies in p-AlGaN interface and a

decrease of oxygen vacancies that can increase hole

concentration in SWNTs.

https://doi.org/10.1016/j.jcrysgro.2020.125738https://doi.org/10.1016/j.jallcom.2020.156177https://doi.org/10.1016/j.matchemphys.2020.123471


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Structural, optical and photoresponse characteristics

of metal-insulator-semiconductor (MIS) type

Au/Ni/CeO2/GaN Schottky barrier ultraviolet

photodetector Department of Physics, Madanapalle Institute of

Technology and Science, Madanapalle, 517 325, Andhra

Pradesh, India

CONACYT–Universidad Juárez Autónoma de Tabasco,

Centro de Investigación de Ciencia y Tecnología Aplicada de

Tabasco (CICTAT), Cunduacán, C.P 86690, Mexico

Department of Physics, Rajeev Gandhi Memorial College of

Engineering and Technology, Nandyal, 518 501, Andhra

Pradesh, India

Instituto de Ciencias Físicas, Universidad Nacional

Autónoma de México, C.P 62210 Cuernavaca, Morelos,

México

Department of Physics, Presidency University, Bangalore,

560064, Karnataka, India

IISER Berhampur, Berhampur, 760 010, Odisha, India

Department of Electronic Science, Kurukshetra University,

Kurukshetra, 136119, India

School of Mechanical Engineering, Yeungnam University,

Gyeongsan, 38541, Republic of Korea

Materials Science in Semiconductor Processing

https://doi.org/10.1016/j.mssp.2020.105190

GaN based metal-insulator-semiconductor (MIS) type

ultraviolet photodetector was fabricated and

investigated using high-k dielectric CeO2 as an

insulating oxide layer. Using XRD analysis, the phase

formation of the as-deposited CeO2 films on GaN was

found to be cubic fluorite. Non-contact mode atomic

force microscopy technique was utilized and explored

the surface morphology of CeO2 films on GaN

composed of prearranged clusters of spherical shape

with an average rms surface roughness of 0.428 μm.

XPS analysis has revealed the existence of two

oxidation states such as Ce3+ and Ce4+ in the Ce3d

spectral envelop. Using absorbance versus wavelength

data, the Tauc's plot was plotted and calculated a

direct optical bandgap of 3.52 eV. The current-voltage

(I–V) characteristics extracted from the device

revealed the symmetric behavior or formation of back-

to-back Schottky barrier at the metal-semiconductor

(MS) interface. Photoresponsivity of the device at +10

V bias was calculated as 28.99 A/W and it is higher

compared to the values extracted from metal-

semiconductor-metal (MSM) type UV PDs reported in

the literature. Furthermore, the transient response

characteristics of the prepared device showed good

stability with almost same rise time and fall time of

~2.73 s and ~5.35 s, respectively. Based on the device

performance, the proposed MIS type structure could

be a suitable for the development of ultraviolet

photodetectors.

Phosphor-free, color-mixed, and efficient illuminant:

Multi-chip packaged LEDs for optimizing blue light

hazard and non-visual biological effects National Institute of LED on Silicon Substrate, Nanchang

University, Nanchang, Jiangxi 330096, China

Optics and Lasers in Engineering

https://doi.org/10.1016/j.optlaseng.2020.106174

Currently many evaluation models on the

photobiological effects (PBE) of light sources do not

consider the influence of age and luminance on the

pupil diameter, which affects the light radiation

intensity on the human retina. In this study, the pupil

diameter is taken into consideration when evaluating

the PBE of several light sources. Moreover, the

correction factor M is proposed. The blue light hazard

(BLH) efficacy and the circadian rhythm (CR) effects of

the daylight at dusk, together with three indoor light

sources with a correlated color temperature (CCT) of

about 3000 K were evaluated by using a corrected

evaluation model. The results show that an

incandescent lamp is more photobiologically friendly

for humans, despite being inefficient. Based on high

wall-plug efficiency (WPE) GaN-based yellow (565 nm,

24.3%@20 A/cm2) and green (522 nm, 41.3%@20

A/cm2) LEDs on silicon substrate, incandescent-like

spectrum and phosphor-free color-mixed white LEDs

(CM-LEDs) with a general color rendering index (CRI)

of 94, a CCT of 2866 K, and an efficiency of 131 lm/W

were manufactured by mixing blue, cyan, green,

yellow and red LEDs. The PBE evaluation results of

such CM-LEDs are superior to those of an incandescent

lamp. Moreover, blue light free and candlelight-toned

LEDs with an efficiency of 120.3 lm/W, a general CRI of

84, a special CRI R9 of 93.3, and a CCT of 1810 K were

fabricated by mixing yellow and red LEDs (R&Y-mixed

LEDs). The R&Y-mixed LEDs show no blue light

weighted quantities and have a weaker influence on

the CR shift. They are photobiologically friendly for

https://doi.org/10.1016/j.mssp.2020.105190https://doi.org/10.1016/j.optlaseng.2020.106174


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humans and suitable for nocturnal indoor and outdoor

lighting environments.

Light Extraction Efficiency Optimization of AlGaN-

Based Deep-Ultraviolet Light-Emitting Diodes The Institute of Technological Sciences, Wuhan University,

Wuhan 430072, People's Republic of China

Center for Photonics and Semiconductors, School of Power

and Mechanical Engineering, Wuhan University, Wuhan

430072, People's Republic of China

State Key Laboratory of Applied Optics, Changchun Institute

of Optics, Fine Mechanics and Physics, Chinese Academy of

Sciences, Changchun 130033, People's Republic of China

ECS Journal of Solid State Science and Technology

https://doi.org/10.1149/2162-8777/ab85c0

Using finite-difference time-domain method, the light

extraction efficiency (LEE) of AlGaN-based deep-

ultraviolet light-emitting diodes (DUV LEDs) is

investigated. Simulation results show that compared

to flat sapphire substrate, the nano-patterned

sapphire substrate (NPSS) expands the extraction

angles of top surface and sidewalls. As a result, the LEE

of transverse-magnetic (TM) polarized light is

improved significantly. Roughening on the backside of

n-AlGaN surface significantly enhances the LEE of top

surface of thin-film flip-chip DUV LEDs. However, the

LEE of sidewalls of thin-film flip-chip DUV LEDs is

greatly weakened. For bare DUV LED, the LEE of flip-

chip LED on NPSS is estimated to be about 15%, which

is around 50% higher than that of thin-film flip-chip

DUV LED with roughening on the backside of n-AlGaN

surface.

Development of polarity inversion in a GaN

waveguide structure for modal phase matching Institute of Photonics and Nanotechnology, Vilnius

University, Saulėtekio ave. 3, 10257, Vilnius, Lithuania

State research institute Center for Physical Sciences and

Technology, Savanorių ave. 231, 02300, Vilnius, Lithuania

Picosun Oy, Tietotie 3, 02150, Espoo, Finland

Journal of Materials Science

https://doi.org/10.1007/s10853-020-04831-z

In this work, we report on the fabrication of a

GaN/AlGaN waveguiding structure dedicated to modal

phase matching, where GaN waveguide has planar

polarity inversion. First, we optimized the growth

conditions for the AlGaN epilayer. Second, on top of

the AlGaN epilayer, we fabricated the waveguiding

structure starting with the growth of the Ga-polar GaN

epilayer followed by atomic layer deposition (ALD) of

an Al2O3 layer, then, continuing with the growth of N-

polar GaN epilayer. We tested several layer

thicknesses, but with 20 nm we managed to inverse

the GaN polarity from Ga to N. To confirm the N-

polarity, we etched the GaN epilayer surface in

aqueous KOH solution. We performed out-of-plane

(0002) and in-plane (11–20) X-ray diffraction and

rocking curve measurements to estimate the

crystalline quality of the AlGaN epilayer, Ga- and N-

polar GaN epilayer. Atomic force microscopy

measurement lets us evaluate the epilayer surface

morphology and roughness. Optical and scanning

electron microscopy inspection revealed

characteristic hexagonal N-polar GaN epilayer surface.

We used high-resolution transmission electron

microscopy to investigate the crystallinity and

orientation of the Ga- and N-polar GaN epilayer, also

the Al2O3 ALD layer, the interface quality of the

waveguide structure.

Ultrahigh Gain of a Vacuum-Ultraviolet

Photodetector Based on a Heterojunction Structure

of AlN Nanowires and NiO Quantum Dots School of Physics, Harbin Institute of Technology, Harbin

150001, China

Interdisciplinary Science Research Center, Harbin Institute

of Technology, Harbin 150001, China

Key Laboratory of Nanodevices and Applications, Suzhou

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

of Science, Suzhou 215123, China

School of Materials Science & Engineering, Harbin Institute

of Technology, Harbin 150001, China

National Key Laboratory of Science and Technology on

Advanced Composites in Special Environments, Harbin

Institute of Technology, Harbin 150001, China

PHYSICAL REVIEW APPLIED

https://doi.org/10.1103/PhysRevApplied.13.064036

Aluminum nitride (AlN) is a promising candidate for

the manufacture of vacuum ultraviolet (VUV)

photodetectors. However, its poor electrical

conductivity limits its applications. Herein, a high-

performance AlN nanowire (NW)-NiO quantum dot

(QD) based VUV photodetector is constructed via a

https://doi.org/10.1149/2162-8777/ab85c0https://doi.org/10.1007/s10853-020-04831-zhttps://doi.org/10.1103/PhysRevApplied.13.064036


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mixed-dimensional strategy. The formation of isolated

nanoscale p-n heterojunctions greatly increases the

concentration of photogenerated electrons, resulting

in an ultrahigh photoconductive gain (9.96) in the AlN

NW-NiO QD material, which is about 27-fold higher

than that of AlN NW (0.368). In addition, the

significant improvement in both photocurrent and

response speed convincingly suggest the great

potential of AlN NW-NiO QD based VUV

photodetectors. Furthermore, the properties of these

photodetectors in an irradiation environment are also

evaluated here. It is found that AlN NW exhibits

excellent anti-irradiation characteristics towards both

electron and proton irradiation, while the AlN NW-NiO

QD material also presents promising potential under

low-dose electron irradiation. This study can be used

as a guideline to design and fabricate high-

performance VUV photodetectors based on wide-

band-gap semiconductors coupled with other

nanostructured systems.

Tunable nanostructured distributed Bragg reflectors

for III-nitride optoelectronic applications Institute of Marine Science and Technology, Shandong

University, Qingdao 266237, China

Department of Microelectronics, Shandong University,

Ji'nan 250100, China

Depth Perception Institute, Jiangsu Industrial Technology

Research Institute, jiangsu, China

Huaian Aucksun Optoelectronics Technology Ltd., Huai'an,

China

RSC Advances

https://doi.org/10.1039/D0RA03569F

Highly reflective and conductive distributed Bragg

reflectors (DBRs) are the key for high-performance III-

nitride optoelectronic devices, such as vertical cavity

surface emitting lasers (VCSELs), but they still suffer

from lack of lattice-matched conductive DBR and

uncontrollable processes. In this work, nanostructured

GaN-based DBRs were fabricated and optimized both

experimentally and simulatively using electrochemical

etching (EC) in different electrolytes using the

transfer-matrix method (TMM) to obtain uniform

wafer scale, highly reflective and conductive reflectors

for the application of GaN-based optoelectronics. The

results revealed that a nanostructured GaN-based

DBR with high reflectivity (>93%) and broad stopband

(∼80 nm) could be achieved in neutral sodium nitrate

by EC, and the nanostructured GaN DBR with a full

visible spectrum range could be designed by tuning

the thickness of the nanostructured GaN DBR layers.

The photoluminescence (PL) and light-out power

enhancements of the GaN-based micro-LED by

incorporating the fabricated nanostructured GaN-

based DBR were 6 times and 150% without the

degradation of electrical performance, respectively,

which contributed to strong light scattering from the

DBR layers. We believe that this work will pave a way

to obtain high-performance GaN-based

optoelectronic devices and guide the applications in

the field of flexible devices and biomedical sensors.

A bow-free freestanding GaN wafer Department of Electronics and Computer Engineering,

Hanyang University, Seoul, Republic of Korea

RSC Advances

https://doi.org/10.1039/D0RA01024C

For applications as high-brightness light-emitting-

diodes, a bow-free freestanding gallium nitride (GaN)

wafer 2 inch in diameter and ∼185 μm in thickness

was fabricated by process-designing pit and mirror

GaN layers grown via hydride-vapor-phase epitaxy,

laser lift-off, N-face polishing of the pit GaN layer, and

three-step polishing of the mirror GaN layer using 3.0

μm-, 0.5 μm-, and 50 nm-diameter diamond abrasives

and by inductively-coupled-plasma reactive-ion

etching. The considerably large concave shape of the

GaN wafer could be decreased by controlling the

removal amount of the Ga-face mirror layer during the

first step of the polishing process, which approached a

bow-free shape or changed with further polishing; this

well correlated with the residual stress of the polished

GaN wafer.

https://doi.org/10.1039/D0RA03569Fhttps://doi.org/10.1039/D0RA01024C


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ELECTRONICS Group leader: Farid Medjoub (CNRS-IEMN)

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

On-Wafer Fast Evaluation of Failure Mechanism of

0.25-μm AlGaN/GaN HEMTs: Evidence of Sidewall

Indiffusion Department of Information Engineering, University of

Padua, 35131 Padua, Italy

United Monolithic Semiconductor, 89081 Ulm, Germany

Fraunhofer Institute for Microstructure of Materials and

Systems (IMWS), 06120 Halle, Germany

IEEE Transactions on Electron Devices

https://doi.org/10.1109/TED.2020.2996983

In this article, we present the results of on-wafer

short-term (24 h) stress tests carried out on 0.25-μm

AlGaN/GaN HEMTs. Devices on-wafer were submitted

to 24-h dc tests, at various gate and drain voltage

values corresponding to dissipated power densities PD

up to 40 W/mm, with estimated channel temperature

≅ 375 °C. GEN1 devices adopted a Ni/Pt/Au gate

metallization and conventional plasma-enhanced

chemical vapor deposition (PE-CVD) SiN passivation; in

GEN2 devices, a modified gate metallization and a

two-layer SiN passivation were adopted. When tested

at Pd >25 W/mm, a substantial decrease of drain

current ID and transconductance gₘ was measured in

GEN1 HEMTs, without any significant shift of threshold

voltage. Failure analysis revealed that Au and O

interdiffusion took place from the sidewalls; Au

gradually substituted Ni as a Schottky contact, while O,

in the presence of high electric field, high

temperature, and high current, promoted (Al)GaN

oxidation and pitting. On the contrary, negligible

degradation was found after high temperature

storage of GEN1 devices without applied bias, up to

450 °C. In GEN2, process modification was effective in

reducing the impact of this failure mechanism,

resulting in only 5% gₘ decrease after 24 h at a

junction temperature of 375 °C with PD = 38 W/mm.

Results demonstrate the effectiveness of the adopted

on-wafer screening methodology in identifying

potentially dangerous failure mechanisms.

Analysis and optimization of GaN based Multi-

channels FinFETs Graduate Institute of Photonics and Optoelectronics,

National Taiwan University, 33561 Taipei, Taipei Taiwan

10617

IEEE Transactions on Nanotechnology

https://doi.org/10.1109/TNANO.2020.2998840

In this work, the design of multi-channels tri-gate

AlGaN/GaN high-electron-mobility transistors

(HEMTs) is optimized for high-power and high-

frequency applications. The application of FinFET

structure has reduced the short channel effect as the

gate length of the device shrinks. But sidewall

depletion of two dimensional electron gas reduces the

current density is another issue to be overcome. Using

multiple AlGaN/GaN channels has been proposed to

compensate the current loss from reduction of

channel width. With a full self-consistent 3D modelling

on carrier transport and heating issues, the design

issue and optimized for multi-channel FinFETs has

been investigated. With a proper design, the

optimized normally-on four channel transistor show a

3.2 times higher maximum transconductance, as

compared to the single channel tri-gate device. And

the performance of unit current gain frequency also

has an improvement in mu

Documents

GaN Technology for Optoelectronics & Electronics...application of the nanoporous GaN-based TP structure for optical sensing. Three-dimensional metal–semiconductor–metal AlN deep-ultraviolet