Zero Read Noise Detectors for the TMT
Don 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
Outline
• Motivation
– Why pursue photon-counting technology?
– Why use Geiger-mode avalanche photodiodes
(APDs)?
• Moore Detector for TMT
• Heritage: LIDAR
• Conclusions
2
Outline
• Motivation
– Why pursue photon-counting technology?
– Why use Geiger-mode avalanche photodiodes
(APDs)?
• Moore Detector for TMT
• Heritage: LIDAR
• Conclusions
3
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
4
Detectivity (higher is better)
SNR 
S

N
signal flux
signal
flux   background flux   (dark noise) 2  (read noise) 2

F tQE
h




 

F tQE   inst A
Fback , tQE   idarkt  N 2read
inst A
h
h

 

inst A

N  tQE
N  tQE  n pix N  ,backgroundtQE  n pixidarkt  n pix N 2read
Sensitivit y  flux at which SNR  1
Detectivit y 
Detectivit y 
1
1

sensitivit y N  , SNR 1
2tQE
1  1  4n pix ( N  ,backgroundtQE  idarkt  N 2read )
5
noise dominated
read

 
tQE
.
N read n pix
Exposure Time to SNR=1
  exposure time to reach a particular SNR. Solve SNR equation for t.

SNR 2 ( N  QE  n pix N  ,backgroundQE  n pixidark )  SNR 4 ( N  QE  n pix N  ,backgroundQE  n pixidark ) 2  4 N 2 n pix (QE N read SNR) 2
2( N  QE ) 2
SNR 1 and N
,background 0 and idark  0
       
N read n pix
.
N  QE
6
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.
read noise
FOM
0
1
2
3
4
5
6
7
Exposure Time (seconds) for SNR = 1
Quantum Efficiency
10%
6,600
7,159
8,486
10,148
11,954
13,830
15,745
17,684
20%
2,300
2,674
3,457
4,363
5,312
6,281
7,259
8,244
30%
1,311
1,591
2,141
2,760
3,402
4,053
4,709
5,368
40%
900
1,123
1,547
2,016
2,500
2,990
3,484
3,979
50%
680
865
1,209
1,587
1,976
2,369
2,764
3,161
mag_star=5, mag_planet=30, R=100, i_dark=0.0010
7
60%
544
703
992
1,309
1,633
1,961
2,291
2,621
70%
453
591
841
1,113
1,392
1,673
1,956
2,239
80%
388
510
730
968
1,212
1,459
1,706
1,954
90%
338
448
645
857
1,074
1,293
1,513
1,734
100%
300
400
577
768
964
1,161
1,359
1,558
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 nonoptical detecting materials
• allow photon counting inside each pixel for
high frame rates and time tagging
• have demonstrated excellent performance for
LIDAR applications
8
Gain of an APD
M
Ordinary
photodiode
Linear-mode
APD
Geiger-mode
APD
100
10
1
0
Response
to a photon
I(t)
Breakdown
M
1
9
∞
Geiger-Mode Imager: Photon-to-Digital Conversion
Pixel circuit
Digital
timing
circuit
photon
Digitally
encoded
photon
flight time
APD/CMOS array
APD
Lenslet
array
Focal-plane
Quantum-limited sensitivity
Noiseless readout
Photon counting or timing
10
Outline
• Motivation
– Why pursue photon-counting technology?
– Why use Geiger-mode avalanche photodiodes
(APDs)?
• Moore Detector for TMT
• Heritage: LIDAR
• Conclusions
11
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 mm pitch imager with streaming, single
photon, readout
12
Moore Photon Counting Imager
Optical (Silicon) Detector Performance
Parameter
Phase 1
Goal
Format
Phase 2
Goal
256x256
1024x1024
25 µm
20 µm
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%
90 K – 293 K
90 K – 293 K
100%
100%
Pixel Size
Read Noise
Operating Temperature
Fill Factor
aProduct
of internal QE and probability of initiating an event. Assumes
antireflection coating match for wavelength region.
13
Moore Photon Counting Imager
Infrared (InGaAs) Detector Performance
Parameter
Phase 1
Goal
Format
Phase 2
Goal
Single pixel
1024x1024
25 µm
20 µm
Read Noise
zero
zero
Dark Current (@140 K)
TBD
<10-3 e-/s/pixel
QEa (1500nm)
50%
60%
90 K – 293 K
90 K – 293 K
NA
100% w/o mlens
Pixel Size
Operating Temperature
Fill Factor
aProduct
of internal QE and probability of initiating an event. Assumes
antireflection coating match for wavelength region.
14
Moore Detector Project Status
• A 256x256x25mm 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.
15
Overview of Pixel Operation
Pixel Architecture
16
ROIC Pixel Layout (2x2 pixels)
metal bump bond
pad
2 pixels, 50 mm
core
(active
quench,
discriminator,
APD latch)
counters (4 pixels)
counter
rollover latch
2 pixels, 50 mm
17
InGaAs Development
• 3 APD designs grown and fabricated
– 2-mm-wide avalanche region (all InP)
– 3-mm-wide avalanche region (all InP)
– 2-mm-wide avalanche region (InGaAs absorber)
• Room-temperature CV measurements made
• Devices in packaging for low temperature
measurements
18
Outline
• Motivation
– Why pursue photon-counting technology?
– Why use Geiger-mode avalanche photodiodes
(APDs)?
• Moore Detector for TMT
• Heritage: LIDAR
• Conclusions
19
Si APD/CMOS Development History
APD’s
1996
Discrete 4x4 arrays
4x4 arrays
wire bonded to
16-channel
CMOS readout
32x32 arrays
fully integrated with
32x32 CMOS readout
not to scale
20
64 x 64 arrays
3D-integrated with
2 tiers of SOI CMOS
256 x 256 arrays
2009
LIDAR Imaging System
Microchip laser
Geigermode APD
array
• Imaging system photon
starved. Each detector must
precisely time a weak optical
pulse.
Color-coded
range image
21
A LIDAR Imaging Detector for NASA
Planetary Missions
Parameter
Current
Goal
Space-Qualifiable
NO
YES
Scalable to Large Format
NO
YES
CMOS ROIC Timing Resolution
250 ps
250 ps
Pixel Size
50 mm
50 mm
unknown
<10-3 e-/s/pixel
Multiplied Dark Current (@140 K)
QE (350nm,650nm,1000nm)a
Operating Temperature
Radiation Limit
Technology Readiness Levelc
•
•
•
•
45%,65%,5%
45%,65%,10%
293 K
90 K – 293 K
unknown
50 Krad(Si)b
2
4
High field
multiplier
Medium
low field
Low
field
absorber
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)
22
32x32 APD/CMOS Array with
Integrated GaP Microlenses
23
Laser Radar Brassboard System
(Gen I)
Taken at noontime on a sunny day
• 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
24
Conventional vs LIDAR Image
Conventional image
25
3D Imaging of Model Airplane
Single Frame
3D Display of Processed Image,
Probability of Detection Color-code
Color-code:
1 m range
display
Airplane hanging
on 6 mm rope
• Multiple-frame coincidence processing of ~3-4 frames removes isolated dark
counts
• Image quality excellent due to low optical cross-talk between pixels
26
Rotatable 3D Images of Multiple Objects
Color-coded by Distance
Color-coded by Detection Probability
• 128x128 images recorded with scanned 4x4 array at 1.06 mm
• Coincidence processed to remove background/dark counts
• Dark blue equivalent to <2 photon average return (right image)
27
Outline
• Motivation
– Why pursue photon-counting technology?
– Why use Geiger-mode avalanche photodiodes
(APDs)?
• Moore Detector for TMT
• Heritage: LIDAR
• Conclusions
28
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.
29