P. Bois

Quantum Quantum Well InfraredWell Infrared DetectorsDetectors

2 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

⇒ Industry (non destructive testing)

⇒⇒⇒⇒ Aerospace (Enhanced Vision System)

⇒ Medical (breast cancer, cardiovascular diseases, ...)

⇒⇒⇒⇒ Defence & Security & Space

Infrared imaging: passive detection, night, all weather

LWIRMWIR

10-3

10-2

10-1

100

101

102

103

104

Spe

ctra

lEm

ittan

ce(W

/m2 /

µm2 3 4 5 6 7 8 9

102

Wavelength (µm)

0.8

0.6

0.4

0.2

0.0

Atm

ospheric Transm

ission

TBB=600 K

TBB=300 K

λλ

d

TdRBB ),(

Nature is perfect ...

Visible

IR EVS

3 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

2004-2010 LW QWIP pictures

THALES640x512 LW QWIP FPAs@ 75K, @ f/2.5 @ 5ms20µm and 25µm pitchNETD = 30 mK

4 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Evolution of IR Imagers

► Reduced Size, Weight And Power : SWAP argument (com pactness)� and cost !

Catherine FC

Catherine QW

Catherine GP

Castor

300 mK 60 mK 180 mK 60 mK

1rst gen | 2ndgen | 3rst gen

Medium range LW IR cameras

(1-3 km)

Thales Optronics

ΝΕ∆Τ :ΝΕ∆Τ :ΝΕ∆Τ :ΝΕ∆Τ :

Single element Scanning Arrays Staring Arrays

► Consequences of the development of staring arrays:� Uniformity and Stability became key constraint� Trade-off on Sensitivity are allowed

5 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Quantum Well Infrared Detectors: Basics

Ga As1-xx

Al Ga As1-xx

Al Ga As

d

∆Ec

+++Silicium

hν

► MBE growth� GaAs substrate � GaAs well� AlXGa1-XAs barrier

Silicon doped

⇒⇒⇒⇒ carriers = electrons

TEM picture

Modulated conduction band⇓⇓⇓⇓

Quantum levels in wells

• Thermal stability

• Uniformity

• 3", 4", … 6" substrates

hνννν

SC SC heterostructureheterostructuren type dopantn type dopant

Silicon

► Intraband transitions

6 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP: Customized spectral detection range

200

50

100

150

400

10060 80 120

20 %

X = 5 %

10 %

E LIE2

40 %

E ETENDU2

Al Ga Asx 1-x GaAs

E

E 2

1

15

20

10

5

E

-

E

(m

eV

)2

1

d ( Å )

( m)

λp

µd

30

0.0

3 4 5 6 7 8 9 11 13 15 18 20

Lambda (µm)

0.0

λoff = 5 µm λoff = 9 µm

λoff = 15 µm

► Quantum engineering� 3 < λ < 80 µm (� THz)

► Resonant spectral shape� ∆λ/λ ≈ 10 %

Lambda (µm)

7 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Short QWIP history: from laboratory objects to products

► late 80's: First QWIPs AT&T Bell Labs (B. Levine)Th-Csf, Martin-Marietta, Lockheed, HRL, US Army Lab, IAF, ACREO, NRC, …

►90's: Focal Plane Arrays Demonstrators – first images

►00's: Equipment, systems and programs

At THOMSON-CSF then THALES

1988 - 1994 : ANALYSE, UNDERSTAND Advantages & Drawbacks

1993 - 1998 : MODELIZE, OPTIMIZE Operating Temperature

1997 - 2000 : REALIZE Laboratory Devices

2000 - 2004 : DEVELOP Focal Plane Array Demonstrators

2004 - : PRODUCE FPAs

8 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

ADVANTAGES:

QWIP Advantages and Drawbacks: 1990's

QUANTUM ENGINEERING⇓⇓⇓⇓

New performances

� Versatility (3 µm →→→→ 20 µm)

� Advanced functionsTunable, Multispectral, Hyperspectral, …

9 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

ADVANTAGES:

QWIP Advantages and Drawbacks: 1990's

� Large substrates (3", 4", …)

� Process and metallurgy mature

� Uniformity ⇒⇒⇒⇒ Performances

� Production yield ⇒⇒⇒⇒ Cost

� Resistance to radiation

III-V TECHNOLOGY (DUALITY)

⇓⇓⇓⇓

Large FPAs

QUANTUM ENGINEERING⇓⇓⇓⇓

New performances

� Versatility (3 µm →→→→ 20 µm)

� Advanced functionsTunable, Multispectral, Hyperspectral, …

10 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Martin Marietta 256 x 256 LW QWIP FPA@ 60 K @F/2.4 @5 ms50µm pitchNETD = 15 mK

LW QWIP pictures: 1991 ���� 1994

1991 : AT&T128 x 128 LW QWIP FPA@ 60K, @ f/2 @ 9ms50µm pitch NETD = 10 mK

11 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

GaAs technology

10 Å

[010]

Up to 6" substrates

III-V Process

MBE epitaxy without mismatch

12 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

ADVANTAGES:

QWIP Advantages and Drawbacks: 1990's

DRAWBACKS:

� Large substrates (3", 4", …)

� Process and metallurgy mature

� Uniformity ⇒⇒⇒⇒ Performances

� Production yield ⇒⇒⇒⇒ Cost

� Resistance to radiation

III-V TECHNOLOGY (DUALITY)

⇓⇓⇓⇓

Large FPAs

� Operating temperature

� Optical couplingINTRABAND TRANSITIONS

QUANTUM ENGINEERING⇓⇓⇓⇓

New performances

� Versatility (3 µm →→→→ 20 µm)

� Advanced functionsTunable, Multispectral, Hyperspectral, …

13 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP R&D studies

► Operating temperature:� Understand photodetection and dark current mechanisms in QWIPs

• Role of contacts, emission /capture,

• Unipolar device,• Steady state / impact ionization,• Electric field distribution,

� Whole device modelling and optimization

� …

► Analyze figure of merits of IR detectors and focal plane arrays� Quantum efficiency and conversion efficiency,� Detectivity D* � NETD, MTF, non uniformity, stability

� …

14 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

• steady state operation ⇒⇒⇒⇒ current is conserved

A

+ + +

+ + +

+ + + + + +

hνννν

Rq g

h=

αν

η(

g exc

trt= τ

QWIPs are "extrinsic" photoconductors

QWIP: Detection mechanisms

15 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

• steady state operation ⇒⇒⇒⇒ current is conserved

A

+ + +

+ + +

+ + + + + +

hνννν

Rq g

h=

αν

η(

g exc

trt= τ

QWIPs are "extrinsic" photoconductors

QWIP: Detection mechanisms

Operation more complex:

Emitter contact is a blocking barrier !

16 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

• steady state operation ⇒⇒⇒⇒ current is conserved

F0 Fi-

1 Fi

Injected current at emitter contact

Capture probability

Optical current

Thermionic current

pcJ J th + Jop

A

+ + +

+ + +

+ + + + + +

hνννν

Rq g

h=

αν

η(

g exc

trt= τ

QWIPs are "extrinsic" photoconductors

QWIP: Detection mechanisms

17 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

►Unipolar device: Only electrons as carriers� No passivation process� No 1/f noise - no drift

QWIP: Unipolar device

0.057

0.056

0.055

Res

idua

l non

uni

form

ity (

%)

6543210Time (Days)

Temporal evolution of the residual non uniformit y T0 Wednesday 9 AM

No activity in the lab Week-end

640x512 LW QWIP FPA

18 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP R&D studies

► Operating temperature:� Understand photodetection and dark current mechanisms in QWIPs

• Role of contacts, Emission /capture,• Unipolar device,• Steady state / impact ionization,• Electric field distribution,

� Whole device modelling and optimization� …

► Analyze figure of merits of IR detectors and focal plane arrays� Quantum efficiency and conversion efficiency,� Detectivity D* � NETD, FTM, dynamics, non uniformity, stability� …

► Optical coupling: convert the initial drawback into new asset� Customized detection band� Multistack detectors� Intrinsic cold filters� …

19 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

MQW

Buffer & Contact

Coupling structure

Thinned substrate

IncomingRadiation

Polarization selection rule forbids normal incidenc e

Intersubband Absorption in MQWs is highly anisotropic

Incoming radiation is not absorbed directly

Only scattered radiation is absorbed

⇒⇒⇒⇒ An artificial coupling scheme is required

The "elementary" pixel of the QWIP FPA is complex.

p ≈≈≈≈ λλλλ

t < λλλλ

p

t

QWIP specificity: Optical Coupling

20 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP specificity: Optical coupling

⇒⇒⇒⇒ artificial way is required for realizing FPAs

Prisms & Corrugated QWIPs: K.K. Choi (1997)

Optical microcavities (Enhanced QWIP): T.R. Schimert (1996)

Antenna coupling structures: W. Beck (1998)

Spiral antenna Jigsaw antenna

21 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP specificity: Diffraction Patterns

Lamellar gratings:K.W. Goossen & S.A. Lyon (1985)

polarisationsensitive

2D gratings:J.Y. Andersson (1991)

Resonant,polarisationinsensitive

Random:G. Sarusi & B. Levine (1994)

broadband for large pixels

Amorphous:TRT (2003)

2D grids:P. Koidl & H. Schneider (1994)

22 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIP players in 2011

► Research Labs:� III-V lab / Univ. Paris 7 (France)� NASA, Jet Propulsion Laboratory (US)� U.S. Army Research Laboratory (US)� Middle East Technical University (Turquie)� NRC, Inst. for Microstructural Sciences (Canada)� Fraunhofer IAF (Allemagne)� …

► Thermal imagers / Systems:� Thales (France, Royaume-Uni): LW – polarimetric - dualband� Flir (US, Sweden): LW� Xenics (Belgique): LW� Aselsan (Turquie): LW� Ircam (Allemagne): LW - dualband� Cantronic (US): LW� Thermosensorik (Allemagne): LW - dualband� Lockheed Martin / Santa Barbara Focalplane (US): LW� NASA, Goddard space flight center (US): VLW - multispectral

QWIP FPA suppliers:� III-V lab/Sofradir (France)� IR Nova (Sweden)� Qmagiq (US)� Qwiptech (US)

� IAF/AIM (Germany)

23 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIPs in production @THALESCatherine-XP

► QWIP array by III-V lab; 384x288 (60 dies per 4" wafer); 25 µm pitch (ROIC ISC0208)

IDDCA VEGA-LW by SOFRADIR (RM4 cryocooler from Thales Cryogenics)

TFPA=75K ���� Tint<5ms ; NETD < 35mKTBB=300K ; f/2.7 ; Dynamic +50K

Camera Catherine-XP by Thales Optronique (France)

768x576 DV-PAL (µscan)

> 2400 arrays

delivered since 2005

24 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

½ TV LW QWIP FPA Statistics

100.0

99.9

99.8

99.7

99.6

99.5

Ope

rabi

lity

(%)

7006005004003002001000

80

60

40

20

NE

TD

(m

K)

7006005004003002001000

IDDCA Index

Responsivity map

@ ± 15 %

99,98 %

30 mK

Volume : > ½ billion pixelsUniformity and reproducibilityWafer yield > 85%

25 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIPs in production @THALESCatherine-MP

► QWIP array by III-V lab full TV format (640x512) ; 20 µm pitch

► ROIC by SOFRADIR

IDDCA SIRIUS-LW by SOFRADIRTFPA=75K ���� Tint<5ms ; NETD < 35mKTBB=300K ; f/2.2 ; Dynamic +50K

Camera Catherine-MP by Thales Optronics (UK)

1280x1024 SXGA (µscan)Polarimetric capabilities

1.2

0.8

0.4

0.0Spe

ctra

l res

pons

ivity

109876Wavelength (µm)

Peak: 8.6 µmFWHM: 0.9 µm

> 900 arrays delivered

since 2006

26 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Other QWIP Products

QWIP Module 3FOV640x480, 320x240

Thermovision SC6000

Star Safire QWIP

• US (Qmagiq)• Sweden (IRNova)

LIRC: Compact Thermal Imager320x240, 640x512

Geminis 110k ML

Taurus 327k L

• Germany (AIM/IAF)

QWIP 640L

QWIP 384 DB

• Germany (AIM/IAF)

27 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIPs: Building blocks for 3rd Gen available

� Very large FPAs : > 1K x 1K ���� enhance resolution

• LWIR, MWIR, VLWIR

• Pitch reduction

� Dual color FPAs ���� get more information

• MWIR/LWIR, LWIR/LWIR

• Pitch reduction

� Polarimetric FPAs ���� get more information

• LWIR, MWIR, VLWIR

• Pitch reduction

28 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Cross section 1 Cross section 2

Dual Band QWIP IDDCA for CATHERINE-XP

SPECTRAL RESPONSE VEGA-MW/LW IDDCA

0%10%20%30%40%50%60%70%80%90%

100%

3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0

Wavelength [µm]

Nor

mal

ized

spe

ctra

l res

pons

e

ααααpeak=20%ααααpeak=40%

Spatial correlation

Reduced cross talk

29 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Dual Band QWIPs

25 µm

(details of a 2 color QWIP array)

Building blocks validated

�Fully compatible with theCatherine-XP casing

�Expected performance at the IDDCA level ( TFPA=73K; T int<7ms ; f/2.7; TBB=300K ; Dynamic +50K):

•LW (8.5µm): NETD < 50mK

•MW (4.6µm): NETD < 35mK

>MW: 4.6µm; FWHM = 0.6 µm>LW: 8.6µm; FWHM = 0.9 µm

>Spectral crosstalk close to zero

384x288 ; pitch 25 µm

ISC0208 ROIC, 1 bump / pixel

���� New dedicated ROIC by Sofradir

Integrate MW Band while Read LW Band

30 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Bispectral : IRCAM Gmbh example

► Camera : Geminis 110k ML� QWIP 384x288 MW/LW 310Hz from IAF / AIM

� Dual FOV f=86mm et f=300mm, 4.4 µm-5.5 µm (MWIR), 7.8 µm-8.8 µm (LWIR)

� NETD < 40mK

31 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

DAY

NIGHT

Figure 2: Dual-band IR images (3000 x 900 pixels) of the city of Freiburg, Germany at daytime (top) and nighttime (bottom). MWIR image and LWIR image are overlayed with complementary colors (not apparent in the grey color print). The panorama images are stitched from approx. 100 single images. IRCAM/IAF/AIM (Germany)

32 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Polarimetric QWIPs

� Polarization imagery gives information about a scene (object reflectivity, emissivity, orientation) which may not be present in the thermal image

� Can be used to help detect objects of interest

� Discriminates artificial objects from natural clutter

� Lamellar grating sensitive to incident polarization and µ-scan, 640x512 x 4 pixels / frame (25Hz)

� Polarimetric contrast > 40 % @20 µm pitch

33 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Polarimetric LW QWIPs : Field trials

Intensity

(thermal image)Polarization contrast

False colorsSuperimposition

34 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Quantum Cascade Detectors (QCD)

► QCD = photovoltaic variation of QWIP for VLWIR and T Hz� no bias � no dark current � higher operating temperature� Modelling ab initio� Expected performances for optimized QCD FPAs suitable for applications

experimentModelling

35 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

•Aopt/Aelec increases, Rep/Idark increases

� Theoretically gain 10 is achievable

� ∆T ≈ +10 K for LWIR detectors

► Doping neutralization outside the absorbing/detecting region:

Optical concentrator: Principle

Cavity with two Bragg mirrors (period λλλλ/2)

Coupling structure for normal incidence waves (period λλλλ)

Optical concentrator (Zero Focal Length superlens)

36 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

QWIPs in 2011

► Dual technology (GaAs based device)� Large size substrate � Large format FPAs

� Uniformity and Yield � Detectors available and affordable

► Unipolar device� No passivation, no 1/f noise - no drift

► Tunable wavelength � MWIR, LWIR and VLWIR range

� Narrow spectral bandwidth

► New functions� Multispectrality,

� Polarimetry

► QWIPs: Attractive physics and devices thanks to bandgap engineeringbut it's a long way to introduce an emergent technology

lab devices to products ⇒ yield, costs, ...

Catherine-XP(Thales Optronique SA)

Catherine-MP(Thales Optronics Ltd)

37 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Many building blocks already achievedmaterial, process,

band gap engineering, modellingphotodetection mechanisms, carrier injection, optical coupling

Physics is well understood

Further studies in progressTechnology enhancement ⇒ increasing fabrication yieldOptical immersion, new quantum structures and specific applications ...

⇒ increasing operating temperatureAdvanced function optimization ⇒ "smart detector"

New steps: More complex quantum heterostructures for advanced functions• 4bands, trispectral/polarimetric, skimming …

• tunable QWIPs, broadband, spectrophotometer, …

• DWELL QWIPs

• QCDs

QWIPs : multidisciplinary R&D topic

38 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Acknowledgements

►Many thanks to …

� QWIP teams in THALES• TRT / 3-5 Lab• Thales Units

� Academic partners• Universities, LETI, ONERA, …

� Industrial partners• Sofradir, Indigo, …

� French and European agencies• DGA, ANR, CNES• ESA

� The worldwide QWIP community

►… and special thanks to Emmanuel !

39 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

►Narrow band for thermal imaging

� No cold filter, emissivity contrast

► contrast

Narrow band / Broadband

Em

issi

vity

λ

Narrow band for imagers

λoff = 5 µm

λoff = 9 µm

λoff = 15 µm

narrow band narrow bandbroadband

Broadband for spectro-imagers

40 | Optoelectronics Rosencher's Day | 24/05/2011 Copyright © 2011 III-V Lab. All rights reserved.

Trispectral polarimetric FPA

9.1 µm

9.1 µm10.4 µm

8.2 µm

S1 S2 VcomS2S1

20 µm

S1 S2 VcomS2S1 S1 S2 VcomS2S1

20 µm

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Nor

mal

ised

spe

ctra

l sha

pe

12.011.511.010.510.09.59.08.58.07.57.0

Wavelength (µm)

Stack 1

Stack 2, grating 1 Stack 2, grating 2