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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