Zero Read Noise Detectors for the TMTDon Figer, Brian Ashe , John Frye, Brandon Hanold, Tom Montagliano, Don Stauffer (RIDL), Brian Aull, Bob Reich, Dan Schuette, Jim Gregory, Erik Duerr, Joseph Donnelly (MIT/LL)

MIT LL No. MS-43282, ESC No. 09-1097

2

Outline

• Motivation– Why pursue photon-counting technology?– Why use Geiger-mode avalanche photodiodes

(APDs)?

• Moore Detector for TMT• Heritage: LIDAR• Conclusions

3

Outline

• Motivation– Why pursue photon-counting technology?– Why use Geiger-mode avalanche photodiodes

(APDs)?

• Moore Detector for TMT• Heritage: LIDAR• Conclusions

4

Why pursue photon-counting technology?• Photon-counting detectors effectively have

zero read noise.• In low light applications, read noise can

dominate signal-to-noise ratio.• Many applications can become low light

applications with higher resolutions.– spectroscopy– time-resolved photometry– fast wavefront sensing and guiding

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Detectivity (higher is better)

.)(411

2yDetectivit

1

ysensitivit

1yDetectivit

1SNRat which flux y Sensitivit

noise) read(noise)dark (flux backgroundflux signal

flux signal

dominated noise read

2,

1,

2,

2,

22

pixreadreaddarkbackgroundpix

SNR

readpixdarkpixbackgroundpix

readdarkbackinstinst

inst

nN

tQE

NtitQENn

tQE

N

NntintQENntQEN

tQEN

NtitQEFh

AtQEFh

A

tQEFh

A

N

SSNR

6

Exposure Time to SNR=1

.

)(2

)(4)()(

for t.equation SNR Solve SNR. particular areach to timeexposure

0 and 0 and 1

2

222,

4,

2

,

QEN

nN

QEN

SNRNQEnNinQENnQENSNRinQENnQENSNR

pixreadiNSNR

readpixdarkpixbackgroundpixdarkpixbackgroundpix

darkbackground

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Example for Planet Imaging

• The exposure time required to achieve SNR=1 is dramatically reduced for a zero noise detector compared to detectors with state of the art read noise.

10% 20% 30% 40% 50% 60% 70% 80% 90% 100%0 6,600 2,300 1,311 900 680 544 453 388 338 300 1 7,159 2,674 1,591 1,123 865 703 591 510 448 400 2 8,486 3,457 2,141 1,547 1,209 992 841 730 645 577 3 10,148 4,363 2,760 2,016 1,587 1,309 1,113 968 857 768 4 11,954 5,312 3,402 2,500 1,976 1,633 1,392 1,212 1,074 964 5 13,830 6,281 4,053 2,990 2,369 1,961 1,673 1,459 1,293 1,161 6 15,745 7,259 4,709 3,484 2,764 2,291 1,956 1,706 1,513 1,359 7 17,684 8,244 5,368 3,979 3,161 2,621 2,239 1,954 1,734 1,558

rea

d n

ois

e

mag_star=5, mag_planet=30, R=100, i_dark=0.0010

Exposure Time (seconds) for SNR = 1

FOMQuantum Efficiency

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Why use Geiger-Mode Avalanche Photodiodes (GM-APDs)?• produce easily distinguishable high voltage

pulse per photon• have zero “excess noise factor”• allow for hybridization and bonding to non-

optical detecting materials• allow photon counting inside each pixel for

high frame rates and time tagging• have demonstrated excellent performance for

LIDAR applications

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Gain of an APD

1

10

100

M

Breakdown0

Ordinary photodiode

Linear-mode APD

Geiger-mode APD

Response to a photon M

1∞

I(t)

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Geiger-Mode Imager: Photon-to-Digital Conversion

Quantum-limited sensitivityNoiseless readout Photon counting or timing

APD

Digitaltimingcircuit

Digitallyencodedphotonflight time

photon

Lensletarray

APD/CMOS array

Focal-plane

Pixel circuit

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Outline

• Motivation– Why pursue photon-counting technology?– Why use Geiger-mode avalanche photodiodes

(APDs)?

• Moore Detector for TMT• Heritage: LIDAR• Conclusions

12

Moore Detector Project Goals

• Operational– Photon-counting– Wide dynamic range: flux limit to 108 photons/pixel/s– Streaming readout

• adaptive optics imaging • multiple target tracking

– Time delay and integrate• Technical

– Backside illumination for high fill factor– Demonstrate 25 m pitch imager with streaming, single

photon, readout

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Moore Photon Counting ImagerOptical (Silicon) Detector Performance

Parameter Phase 1 Goal

Phase 2 Goal

Format 256x256 1024x1024

Pixel Size 25 µm 20 µm

Read Noise zero zero

Dark Current (@140 K) <10-3 e-/s/pixel <10-3 e-/s/pixel

QEa Silicon (350nm,650nm,1000nm) 30%,50%,25% 55%,70%,35%

Operating Temperature 90 K – 293 K 90 K – 293 K

Fill Factor 100% 100%

aProduct of internal QE and probability of initiating an event. Assumes antireflection coating match for wavelength region.

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Moore Photon Counting ImagerInfrared (InGaAs) Detector Performance

Parameter Phase 1 Goal

Phase 2 Goal

Format Single pixel 1024x1024

Pixel Size 25 µm 20 µm

Read Noise zero zero

Dark Current (@140 K) TBD <10-3 e-/s/pixel

QEa (1500nm) 50% 60%

Operating Temperature 90 K – 293 K 90 K – 293 K

Fill Factor NA 100% w/o lens

aProduct of internal QE and probability of initiating an event. Assumes antireflection coating match for wavelength region.

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Moore Detector Project Status

• A 256x256x25m readout integrated circuit is being fabricated.

• InGaAs test diodes are being fabricated.• Silicon GM-APD arrays have been fabricated and will

be bump-bonded to the new readout circuit.• Photon-counting electronics are being built.• Testing will begin later in 2009.• Depending on results, megapixel silicon or InGaAs

arrays will be developed.

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Overview of Pixel OperationPixel Architecture

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ROIC Pixel Layout (2x2 pixels)

2 pixels, 50 m

2 p

ixe

ls, 5

0

m

metal bump bond pad

core(active quench, discriminator, APD latch)

counter rollover latch

counters (4 pixels)

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InGaAs Development

• 3 APD designs grown and fabricated– 2-m-wide avalanche region (all InP)– 3-m-wide avalanche region (all InP)– 2-m-wide avalanche region (InGaAs absorber)

• Room-temperature CV measurements made• Devices in packaging for low temperature

measurements

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Outline

• Motivation– Why pursue photon-counting technology?– Why use Geiger-mode avalanche photodiodes

(APDs)?

• Moore Detector for TMT• Heritage: LIDAR• Conclusions

20

Si APD/CMOS Development History

1996 2009

APD’s Discrete 4x4 arrays

4x4 arrays wire bonded to

16-channel CMOS readout

32x32 arraysfully integrated with 32x32 CMOS readout

64 x 64 arrays 3D-integrated with 2 tiers of SOI CMOS 256 x 256 arrays

not to scale

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• Imaging system photon starved. Each detector must precisely time a weak optical pulse.

Microchip laser

Geiger-mode APD array

Color-codedrange image

LIDAR Imaging System

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A LIDAR Imaging Detector for NASA Planetary Missions

• These arrays will be fabricated for back-illumination with bump bonding, enabling high performance in a space-qualifiable focal plane.

• The design of the ROIC will be finished by the end of 2009, with fabrication starting in early 2010.

• Funding: $546,000 • Duration: 3 years (2008-2010)

Low field

High fieldmultiplier

Medium low field

absorber

Parameter Current Goal

Space-Qualifiable NO YES

Scalable to Large Format NO YES

CMOS ROIC Timing Resolution 250 ps 250 ps

Pixel Size 50 m 50 m

Multiplied Dark Current (@14 K) unknown <10-3 e/s/pixel

QE (350nm,650nm,1000nm)a 45%,65%,5% 45%,65%,10%

Operating Temperature 293 K 90 K – 293 K

Radiation Limit unknown 50 Krad(Si)b

Technology Readiness Levelc 2 4

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32x32 APD/CMOS Array with Integrated GaP Microlenses

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Laser Radar Brassboard System (Gen I)

• 4 4 APD array• External rack-mounted timing circuits• Doubled Nd:YAG passively Q-switched microchip laser

(produces 30 µJ, 250 ps pulses at = 532 nm)• Transmit/receive field of view scanned to generate 128 128 images

Taken at noontime on a sunny day

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Conventional vs LIDAR Image

Conventional image

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3D Imaging of Model Airplane

• Multiple-frame coincidence processing of ~3-4 frames removes isolated dark counts

• Image quality excellent due to low optical cross-talk between pixels

Airplane hanging on 6 mm rope

Color-code:1 m range display

3D Display of Processed Image,Probability of Detection Color-code

Single Frame

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Rotatable 3D Images of Multiple Objects

• 128x128 images recorded with scanned 4x4 array at 1.06 m• Coincidence processed to remove background/dark counts• Dark blue equivalent to <2 photon average return (right image)

Color-coded by Distance Color-coded by Detection Probability

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Outline

• Motivation– Why pursue photon-counting technology?– Why use Geiger-mode avalanche photodiodes

(APDs)?

• Moore Detector for TMT• Heritage: LIDAR• Conclusions

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Conclusions

• Large-format photon-counting imaging detectors are within reach.

• We are funded to make 256x256 and megapixel devices.

• A 256x256 detector silicon-based array should be in testing by the end of the year.

• The devices will be implemented in a broad range of low light level and LIDAR timing applications.