Next Generation of Terahertz Sources and · PDF fileNext Generation of Terahertz Sources and Detectors. ... Center for Terahertz Science and Technology ... effect transistor

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DARPADARPAMicrosystems Technology Office

MTOMTO

Dr. Edgar J. MartinezProgram Manager

Microsystems Technology Office

3701 N. Fairfax Drive Arlington, VA 22203Tel. (703) 696-7436

[email protected]

Next Generation of Terahertz Next Generation of Terahertz Sources and DetectorsSources and Detectors

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E/M Attenuation vs FrequencyE/M Attenuation vs FrequencyLimitations of Current TechnologyLimitations of Current Technology

AT

TE

NU

AT

ION

(D

B/K

M)

1000

100

10

1

0.01

0.1

10 GHz3cm

1003mm

1030µ

1 THz0.3mm

1003µ

10000.3µ

SubmillimeterMillimeter Infrared Visible

FREQUENCYWAVELENGTH

H2O

H2O

O2

CO2

O2CO

2

O3

H2O

H2O. CO2

H2O

Heavy Rain(25mm/h)

Drizzle(0.25mm/h)

H2O

20oC1ATM

H2O : 7.5g/m3

Visibility 50m

Fog (0.1g/m3)

Excessive Rain(150mm/h)

Terahertz

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Using a limitation to our advantage!!!Using a limitation to our advantage!!!

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Program ObjectivesProgram Objectives

Explore innovative semiconductor device and circuit concepts for the demonstration of high power sources and high sensitivity detectors for the region of the electromagnetic spectrum between 0.3-10 THz (1 - 0.03 mm)

Frequency (Terahertz)

Pow

er, W

atts

“Technology Gap”

Lead Salts

III-Vs

II-V1s

Phototonic

0.01 0.1 1 10 100 1000

Impatt

Gunn

10010

1100m

10m

1m

100µ

10µ1µ

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Technical ChallengesTechnical Challenges

THz SourcesTHz Sources�Achievement of high output power (at least mWs)�Efficiency�Compactness�Tunnability for certain applications

THz DetectorsTHz Detectors�High Sensitivity and Detectivity�Quantum Efficiency�Compactness

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• InP-and Sb-based HEMTs

• GaN-based Gunn diodes

• Sb-based Stark Ladders and Quasi-optic Combiners

• Passives and Wave-guides

• Optical Photomixing

• SiGe VCSELs

THz DetectorsTHz Sources

Technical ApproachesTechnical Approaches

5D\WKHRQ�6\VWHPV�&RPSDQ\

ElectricalElectrical OpticalOptical • RTD-based

• Electro-acoustic Detectors (HEMTs)

• Photon assisted tunneling in QWs

• RTD-based

• Electro-acoustic Detectors (HEMTs)

• Photon assisted tunneling in QWs

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APPROACH:• Develop high performance HEMTMMIC sources with integrated antennasfor 0.3 THz to 1 THz frequency range

• Develop novel superlattice oscillatorsand multipliers for 1 THz to 10 THz frequency range

OBJECTIVE:Develop monolithic integrated circuits capable to generate power at 0.33 THz, 0.66 THz, 1 THz and 3 THz.

APPLICATIONS:•Remote sensing•High resolution imaging•High data-rate space communication

State of the art HEMT MMIC

Quantum Device Technologies for Quantum Device Technologies for THz Communications and ImagingTHz Communications and Imaging

Quasi-optical superlattice array for harmonic generation

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0.3 THz to 1 THz SOURCES0.3 THz to 1 THz SOURCES

X2

Oscillator Amplifier ActiveDoubler

Amplifier Antenna

165 GHz 165 GHz 0.33 THz 0.33 THz 0.33 THz

X2

Oscillator Amplifier ActiveDoubler

Amplifier

165 GHz 165 GHz 0.33 THz 0.33 THz

Amplifier

0.33 THz

X3

ActiveTripler

X3

1 THz

Antenna

1 THz

CHALLENGES• MMIC design

• Low-loss passive components– Antennas

– Transmission lines– Power combiners

• Spatial power combining• Packaging

• Testing

CHALLENGES• MMIC design

• Low-loss passive components– Antennas

– Transmission lines– Power combiners

• Spatial power combining• Packaging

• Testing

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InAsInAs//AlSbAlSb//GaSbGaSbMaterials EffortMaterials Effort

HEMT MMIC

1 THz

x 3

3 THz(1-10 THz)

SuperlatticeHarmonicGenerator

Antenna

3 THz

Quasi-optical superlattice arrayfor harmonic generation

• 1-10 THz source development

- collaboration with UCSB (Allen)

- InAs/AlSb superlattice devices

- emphasis on harmonic generation

• Materials support for Raytheon (Frazier)

- RTD structures

- High Jp

- IMSC MBE Capability

• 1-10 THz source development

- collaboration with UCSB (Allen)

- InAs/AlSb superlattice devices

- emphasis on harmonic generation

• Materials support for Raytheon (Frazier)

- RTD structures

- High Jp

- IMSC MBE Capability

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OBJECTIVE:Develop and demonstrate an electrically excited solid-state Terahertz sources, capable of delivering >1 mW of power in the range above 1 THz

APPROACH:•Implementation of InAs/AlSb superlattice, Stark ladders for THz generation•Implementation of Quasi-optic arrays for power combining•Demonstration of THz harmonic generation

OBJECTIVE:Develop and demonstrate an electrically excited solid-state Terahertz sources, capable of delivering >1 mW of power in the range above 1 THz

APPROACH:•Implementation of InAs/AlSb superlattice, Stark ladders for THz generation•Implementation of Quasi-optic arrays for power combining•Demonstration of THz harmonic generation

Solid State Terahertz Sources for Solid State Terahertz Sources for Sensing and Satellite CommunicationsSensing and Satellite Communications

THz

InAs/AlSbSuperlattice in an electric field

THz Cavity

Inductive grid

Superlattice inCapacitive grid

Center for Terahertz Science and Technology

UC Santa Barbarahttp://www.qi.ucsb.edu/

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SolidSolid--State Terahertz Sources State Terahertz Sources

TECHNICAL APPROACH:

• Unique approach combining new semiconductor and micromachined concepts

• Semiconductor device potential for high-power fundamental or harmonic sources

• Possibility to apply micromachined concept to other sources developed under this program

TECHNICAL APPROACH:

• Unique approach combining new semiconductor and micromachined concepts

• Semiconductor device potential for high-power fundamental or harmonic sources

• Possibility to apply micromachined concept to other sources developed under this program

+ =× nGaN NDR Diodesfor THz signal Generation

Micromachined Resonator; Filter/Multiplier

Solid-State Terahertz Source

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E [eV]

k [cm-1]

EG=3.4eV

ENDR=5.6Inflection point

Electron transfer

50-µm Series GaN NDR Diode 30-µm Shunt GaN NDR Diode

OBJECTIVE:Take advantage of the electron transport and material properties of III-N semiconductors for the demonstration of Gunn diode THzsources

CHALLENGES:•Achieve good quality GaN materials •Demonstrate NDR performance in WBG semiconductors•Demonstrate generation of THzradiations

IIIIII--N TerahertzN Terahertz GunnGunn DiodesDiodes

600Field [KV/cm]

Vel

ocit

y [1

07cm

/sec

]

0 100 200 300 400 5000

0.5

1

1.5

2

2.5

3GaN

GaAs

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“Split-Block” formation of micromachinedwaveguide array

Loop

FGC

Passive Silicon Micromachined Structures Passive Silicon Micromachined Structures for THz Applicationsfor THz Applications

APPROACH:

Use Silicon Micro-machining

Technology for the Development of:

• THz waveguides for high-performance

low-loss circuits

•Electric and magnetic transitions from

planar transmission lines to micromachined

waveguides

• Transitions between waveguides and

planar micromachined antennas

•Compact resonators for GaN Gunn sources

APPROACH:

Use Silicon Micro-machining

Technology for the Development of:

• THz waveguides for high-performance

low-loss circuits

•Electric and magnetic transitions from

planar transmission lines to micromachined

waveguides

• Transitions between waveguides and

planar micromachined antennas

•Compact resonators for GaN Gunn sources

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OBJECTIVES:

TECHNICAL APPROACH:

AllAll--SolidSolid--State Photomixing TransmitterState Photomixing Transmitter

Develop a solid-state source for the THz region having up to 1 mW output power and:

• Stable continuous-wave performance• Room-temperature operation• Tunability up to ~1 octave• Instantaneous frequency stability > 1:106

• Phase lockability (required for comms)• Good beam characteristics

(TEM000 Gaussian desirable)

•Optical mixing in an ultrafast photoconductor (LT-GaAs) •Couple internal THz photocurrents to a THz load (antenna)• Implementation of power combining techniques

ω 3 beamω 3 beam

h ν 1

h ν 2

R/2

R/2

PumpBeams

P3 =R

2η1λ1η 2λ 2

eghc

2 P1

P2

1+ ω3

τ( )2

1+ ω3

RC( )2

Photomixer element

High-ρ SiSubstrate

Fiber-optic template(micromachined Si)

ν1+ν2

Fiber amps &phase shifters

Starcoupler

|ν2-ν1|

Binary-optical lenslets

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OBJECTIVE:

To demonstrate a SiGe, micro-disk cavity, intersubband laser suitable for communication systems

APPROACH:

•Silicon micromachining for novel resonator design•SiGe unipolar architecture•E/M simulation for device optimization•1-10 THz operation

Quantum well transitions between E3 and E2. Proposed device will use SiGe quantum wells and hole intersubband transitions.

Pedestal

Si Substrate

WhisperingGalleryResonator

Active Layer

Radiation Radiation

Micro-disk lasers

THzTHz Sources Based onSources Based on IntersubbandIntersubbandTransitions inTransitions in SiGeSiGe Quantum WellsQuantum Wells

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Vertical Cavity SiliconVertical Cavity Silicon--Germanium Quantum Germanium Quantum Cascade Lasers for Terahertz EmissionCascade Lasers for Terahertz Emission

OBJECTIVE:Develop and demonstrate a vertical cavitySiGe quantum cascade laser capable to operate in the THz region of the electromagnetic spectrum

APPROACH:

•Characterization of ISB lifetimes in p-SiGe QWs

•Demonstrate FIR emission in p-SiGetunnel barrier structures

•Demonstrate surface emission in p-SiGequantum cascade structures

•Demonstrate vertical cavity SiGe quantum cascade device

injector states

injector states

Active Region

Injector

Infrared emission

Schematic and band diagram for SiGe QC

Laser

SiGe VCSEL

p-Sisubstrate

Si1-xGex buffer: x= 0-0.25

Si0.5Ge0.5

Si0.5Ge0.5

Si0.5Ge0.5

p-Si barrier

p-Si barrier

Surface emission

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OBJECTIVE:

• Develop high-sensitivity, solid-state RF detector

MMICs for the 0.3 - 3 THz frequency band.

DOD FUTURE USES:• Man-portable, ultra-secure

THz communication links• Space-based imaging of

upper atmosphere

• Phased array missile seekers/munitions

SolidSolid--State Terahertz Detector TechnologyState Terahertz Detector Technology

APPROACH:

•Design and develop low-parasitic InP & GaSb resonant tunneling diodes (RTDs)

•Use epitaxial transfer to integrate RTDs with low-loss THz antenna structures.

•Demonstrate passive and super-regenerative RTD detector-antenna MMICs

•Demonstrate simplex THz communication link.(with HRL & UCSB)

HIGH-SENSITIVITYACTIVE THz DETECTORS

HIGH-SENSITIVITYACTIVE THz DETECTORS

RTD

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Plasma Wave Terahertz ElectronicsPlasma Wave Terahertz Electronics

OBJECTIVES:

•Demonstrate resonant terahertz detector with high sensitivity•Observe terahertz radiation from a field effect transistor•Explore applications of plasma wave electronics to silicon

APPROACH:

•Implement detectors using GaN based HEMTs•Increase the growth of plasma waves using resonant tunneling structure•Use “light” electrons in deep submicron silicon

Source Drain

GateRT structure

0.05 µm

0.1 µm

Enhanced detectivity in sub-micron HEMT structures

0.025 µm

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THz Molecular InteractionsTHz Molecular Interactions

TECHNICAL CHALLENGES:

•Specific identification of chemical species•Quick response (< 1 second)•Small (<< 1 ft3)•Low Power•Simple-Based on FASSST Concept•Potentially Inexpensive in Quantity

OBJECTIVE:

Build test bed for compact THz sources and detectors.

Experimentally determine rotational energy level spectrum of various gas phase molecules

Absorption Cell

Gunn Diode/MultiplierSource

Diode Detector

Power Supply Sweep ControlSignal Acquisitionand Processing

10 cm

FASSST Point-Sensor Test Bed

10 GHz of the Spectrum of ClONO3 recorded with OSU FASSST Spectrometer

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top QWcontact(source)

control gate

topdepletiongate

bottomQW

contact(drain)

bottom QW

top QWtunneling

back depletiongate

< 2 µm

quantized2D electronlayers

THz radiation

Double quantum well THz detector

concept

back control gate

top control gate

backdepletiongate

backdepletion

gate

2DEGcontact

2DEGcontact

topdepletion

gate

topdepletion

gate

Several bowtie DQW detectors have been fabricated

back control gate

top control gate

backdepletiongate

backdepletion

gate

2DEGcontact

2DEGcontact

topdepletion

gate

topdepletion

gate

Several bowtie DQW detectors have been fabricated

THz Detection Based on PhotonTHz Detection Based on Photon--assisted assisted Tunneling on Double Quantum WellsTunneling on Double Quantum Wells

kx

ky

EeVSD

µ1

µ2

photon∆E0occupiedstates

inhighdensityQW

unoccupiedstatesinlowdensityQW

photon

photonOBJECTIVE:

Demonstrate tunable, narrowband photon-assisted tunneling in double quantum well (DQW) heterostructures.

TECHNICAL APPROACH:

• Use bandgap engineering to optimize photodetectorperformance.

• Develop antenna structure compatible with THz detectors

• Bench-demonstration of THz detector system

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SummarySummary

• Environmental sensing

• Upper-atmosphere imagery

• Covert satellite communications

• Chem/Bio Detection (Near Distance)

DARPA is Creating Future Opportunities DARPA is Creating Future Opportunities forfor THzTHz Technology in:Technology in:

Documents

Next Generation of Terahertz Sources and · PDF fileNext Generation of Terahertz Sources and Detectors. ... Center for Terahertz Science and Technology ... effect transistor