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

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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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Detector 10G44092-K03

Element Dark Current at 9.3V

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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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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

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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