IR Detectors Developments for Space Applications
Harald WellerSELEX GALILEO Infrared Ltd, Southampton, UK
CMOS Image Sensors for High Performance Applications
Toulouse, France, 6th & 7th December 2011
SELEX GALILEO Southampton
• Nearly 50 years experience in research and developm ent
• Vertically integrated, Southampton’s manufacturing starts from basic elements Hg, Cd and Te
• Experienced in growing and processing a range of semiconductor materials (PC and PV technologies)
• Clean room capacity and infrastructure to run highe r volumes (11,200 m² facility of which 3,200 m² are cle an rooms)
• Design of custom integrated read out circuits
• Site highly specialised in packaging and testing of sensors (including cryogenics) with capability of moving in to adjacent sensor markets
• Developing electronics design capability
RECENT PROJECTS – SPACE APPLICATIONS
• MTG pre-development (2006-2010, concluded)
• ESA-APD (2008-2011, concluded)
• Sentinel 3 pre-development (2006-2007, concluded)
• METimage pre-development (on-going)
• ESO Gravity (on-going)
• ESA Large Format Near InfraRed (LFNIR)
Evolution of APDs at SELEX-GALILEO
320x256, 2D, (SWIFT)
320x256, Multifunctional,Thermal, 2D, 3D and Range Finder
320x256, 2D and 3D, (SWALLOW)
320x256, 2D and Thermal Mode, (SWAN )
320x256, SW, High Speed, (SAPHIRA)
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2011MAJOR TRIALS
International
Airborne
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Bias volts
Ava
lanc
he g
ain 2.5 µm
3 µm
3.5 µm
4 µm
4.5 µm
SW APD - Application areas
Cut-off wavelength
Burst Illumination LIDAR (BIL)
imaging
Low background flux applications
Photon counting or linear mode detectors
HgCdTe Avalanche Photodiode Detector with >2 um Cut-off Wavelength
ESA/ESTEC Contract 21751/08/N/EM
ESA APD – Objectives
Objectives of Contract •Design and manufacture a mercury cadmium telluride (MCT) avalanche photodiode (APD) detector and Transimpedance (TIA) pre-amplifier circuit such that the MCT APD/TIA combination meets a set of performance criteria suitable for a LIDAR receiver
•Test and characterise the MCT-APD/TIA
Why use MCT for Avalanche Photodiodes?•Near-ideal single-carrier cascade avalanche
– “almost noiseless” gain in the pixel
•Composition-tuneable bandgap – suitable for many IR wavelengths
ESA APD - Construction: Encapsulated Detector
Final Device
Preamp DieHybrid
Metallised Leadout Encapsulation
ESA APD - Performance Criteria
Parameter Value
Operating wavelength 2051 nm
Detector quantum efficiency > 70%
Active area diameter > 150µm
Excess noise factor (F) <1.5
Operating temperature > 200 K
Input signal/dynamic range. minimum: 8000maximum: 2E6
Bandwidth >20 MHz
NEP < 100 fW/√Hz
Gain stability 0.1% rms.
Linearity 5% rms
Total ionizing dose 5 krad (Si) minimum
Proton irradiation 1E10 p/cm2
Summary of Performance Demands
ESA APD - Performance Summary
Summary Conditions:Low flux: 7.9kphotons/50ns/pixel from 1000K Blackbody SourceAvalanche Bias: 9.25 ± 0.05 Volts reverse biasSignal Frequency: 500Hz (mechanical chopper)Noise frequency: 500kHz (10kHz measurement bandwidth)
Device Identity
Low Flux Signal Low Flux Noise White Noise(No flux)
Low Flux QE* NEP
mV nV/√Hz nV/√Hz - fW/√Hz
4720-E05 6.84 73 54 1.02 63
4721-G08 6.02 164 70 0.93 87
44092-L01 7.11 112 54 0.89 58
44092-M01 6.63 114 65 0.87 74
44092-I02 9.65 245 150 0.94 120
44092-J02 7.90 161 82 0.83 83
44092-K01 6.20 96 52 0.92 65
44092-K03 7.20 130 62 0.89 69
HgCdTe Avalanche Photodiode Detector with >2 um Cut-off Wavelength
Radiation Testing
ESA APD - Dark Current: Whole Pixel
Dark Current
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Diode Bias (V)
Ele
men
t Dar
k C
urre
nt(n
A)
Detector*
Detector 10G44092-K03
Element Dark Current at 9.3V
bias(nA)
Before Radiation
After Radiation
4720-E05 38 47
4721-G08 160 160
44092-L01 170 170
44092-I02 880 860
44092-J02 500 430
ESA APD - Total Ionising Dose
44092-L01 5kRad (Si)
Before After Change Units
Signal 7.11 6.22 12% mV
Noise (Low Flux) 112 111 1% nV/√Hz
Noise (Blind) 54 52 4% nV/√Hz
Gain 6.64 5.85 12% -
Cut-off 2.583 2.574 0.3% µm
NEP 58 63 - fW/√Hz
4720-E05 10kRad (Si)
Before After Change Units
Signal 6.84 6.24 9% mV
Noise (Low Flux) 73 75 3% nV/√Hz
Noise (Blind) 54 40 26% nV/√Hz
Gain 5.56 5.29 5% -
Cut-off 2.618 2.614 0.2% µm
NEP 63 50 - fW/√Hz
Facility: ESTEC Co-60, Noordwijk, NetherlandsDose rate: 2.5 krads/hr (approx)Condition: Powered, biased, room temperatureTime between irradiation and test: 15 days
ESA APD - Proton
Device ID: 44092-I02
Dose: 1 × 1010 p+/cm², 10MeV eq.
Before After Change Units
Signal 9.65 12.8 32.9% mV
Noise (Low Flux) 245 219 10.6% nV/√Hz
Noise (Blind) 150 94 37.5% nV/√Hz
Gain 8.49 11.3 33.3% -
Cut-off 2.57 2.595 1.0% µm
NEP 124 57 - fW/√Hz
Device ID: 44092-J02
Dose: 3 × 1010 p+/cm², 10MeV eq.
Before After Change Units
Signal 7.9 11.2 42.1% mV
Noise (Low Flux) 161 115 28.7% nV/√Hz
Noise (Blind) 82 54 33.8% nV/√Hz
Gain 7.9 11.0 39.0% -
Cut-off 2.611 2.612 0.0% µm
NEP 83 38 - fW/√Hz
Facility: PSI, Villigen, SwitzerlandDose rate: 1 × 10¹º protons/cm², 3× 10¹º protons/cm² (10MeV eq.).Condition: Unpowered, room temperatureTime between irradiation and test: 57 days
ESA APD - Summary
•“Novel” approach of hybridising diode directly to TIA preamplifier has been successful
•Device is sensitive to primary wavelength (2.051µm) but also suited to other wavelengths (1.3µm to 2.2µm)
•The device exceeds the key performance criterion (NEP<100fW √Hz)
•Most other performance criteria achieved (though some not fully demonstrated)
•Manufacturing method for diode established. Viability of manufacturing demonstrated – yields sustainable
•Encapsulated detector designed (and available for breadboard activities)
•Exploitation of device in LIDAR system yet to be demonstrated
SW APD
MCT APD for Wavefront Sensors and Interferometry
Uniformity of avalanche gain
Normalised laser signal as function of avalanche g ain
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Pixel number
Out
put s
igna
l (m
V)
Gain - x14
Gain - x28
Gain - x38
Avalanche gain adds virtually nothing to non-unifor mity
Depends only on voltage and alloy composition
Wavefront sensors and interferometry
Typical requirements:
• Avalanche gains x10 to x30• Waveband in region of 1.0 to 2.5µm - mainly J,H and K
band• 256x256 array• Frame rate >1KHz• Sensitivity <3e rms at pixel rate of 5MHz/channel• 24µm pixel size• Multiple readout windows with independent reset• Low noise floor• Non-destructive readout • 32 parallel outputs• Temperature range 30K to 80K
Acknowledgements:All the data presented here is courtesy of European Southern Observatories, ESO
With special thanks to Dr Gert Finger
SW APD evaluation at ESO
APD sensorSELEX-Galileo Swallow 3D detectorOperated in simple non-destructive read modeVoltage controlled avalanche gain2.5µm cutoff arrays
ESO APD test kitCooled optics for few photons imagingCryogenic symmetric pre-amplifierTwo stage engine to 30K
Typical exposure
Avalanche gain versus bias voltage
ROIC ME788Cutoff wavelength - 2.45 µm Temperature - 40K
black diamonds: measuredexponential dependenceon bias voltage
model
Data courtesy of ESO
Noise histogram with eAPD
APD sensor
ROIC ME788Cutoff - 2.45 µm Temperature - 40KInt. time – 5.06msBandwidth – 5MHzAPD gain – 33x
Data courtesy of ESO
9.3 e/pixel test pattern versus APD gain
APD sensor
ROIC ME788Cutoff wavelength - 2.45 µm Temperature - 40KIntegration time – 5.06msBandwidth – 5MHz
Optics
Filter K shortPattern contrast – 9.3 e/pixel
Data courtesy of ESO
1.75 e/pixel sensitivity with APD gain of 33
APD sensor
ROIC ME788Cutoff wavelength - 2.45 µm Temperature - 40KIntegration time – 5.06msBandwidth – 5MHzAPD gain – 33x
Optics
Filter K shortPattern contrast – 1.75 e/pixel
Signal processing
Double correlated clamp16 frames averaged
Data courtesy of ESO
SW APD Fowler sampling
• number of nondestructive readouts increasing with integration time
• 5.06 ms /frame • 2.7 erms 1 Fowler pair (DCS)• noise ∝∝∝∝• integration time 42 ms
1.2 erms 8 Fowler pairs • for integration time ≥≥≥≥ 50ms
shotnoise = with I dark=84 e/s
• for λλλλc=2.65 µµµµm HgCdTe50 ms integration time possible without limitingsensitivity by shot noise
Data courtesy of ESO
SW APD Excess Noise Factor
• excess noise close to unityfor APD gain up to 33
• excess noise determined form ratio of photometric gain and gain obtained from photon transfer curve
Data courtesy of ESO
Noise Histogram of SW APD
• ADP gain 33• 5 MHz/channel
Data courtesy of ESO
Conclusions from pre-development study
Sensitivity <3e rms is achievable using HgCdTe eAPD s for imaging in J H and K bandwith 5MHz clock and >1KHz frame rate
SELEX-Galileo were down-selected to supply sensors for the GRAVITY Programand contracted to design a custom ROIC
APD sensors in the VLT Interferometer
European Southern Observatories, ESOVery Large Telescope, VLT – cluster of four 8.2m uni t telescopes
The SW infrared APD detectors
Critical to the GRAVITY system are the four infrared wavefront sensors and one fringe tracker to correct the atmospheric turbulence at each telescope, and stabilise the fringe phase in the VLTI beam relays.
VLTI requirements
• Adaptive optics needed to correct for atmospheric distortion using embedded sources (galactic center).
• The IRIS instrument is used for simultaneous first order wavefront corrections (tip-tilt) of all 4 telescopes on a single detector
APD wavefront sensor :
• 256x256 array at K band• Frame rate >1KHz• Sensitivity <3e rms at 5MHz• 32 parallel outputs• 24µm pixel size• Non-destructive readout
96x96
GRAVITY Full Custom ROIC - SAPHIRA
General architecture320x256 on 24µm pitch with either 32, 16, 8 or 4 ou tputs
Pixel mapping32 outputs organised as 32 sequential pixels in row (ie row scan requires 10 clocks).
WindowingMultiple windows each independently resettable
ReadoutNon-destructive readout with internal glow protecti on permitting Fowler sampling with a large number of readouts to reduce readout n oise to <1 e rms
Full custom pixelDesigned for low intrinsic noiseVariable integration capacitorVoltage clamp to minimise persistenceGlow protectionAPD protection circuit15fF integration node capacitance
SAPHIRA - full custom ROIC for GRAVITY
1 2 3 420 19 18 17
3231
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1211
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SAPHIRA
Summary of eAPD arrays
SAPHIRA
• Low Photon Flux Imaging
• Spectroscopy
• Ultra fast framing
SWIFT - Multifunctional Array
• 2D and 3D Burst Illumination LIDAR
• Thermal and low light level imaging
• Scene-based laser range finding
Conclusions
• Benefits of SW APD for LIDAR receiver applications were demonstrated
• APD radiation results obtained
• Existing SW APD technology independently characteri sed,
demonstrating sensitivity of <3e rms
• Gravity custom ROIC for SW APD in development
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