characterization of a large format hgcdte on silicon focal plane array b. hanold, j. lee, d. figer...
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Characterization of a Large Format HgCdTe on Silicon Focal Plane Array
B. Hanold, J. Lee, D. Figer – Rochester Institute of TechnologyL. Mears, J. Bangs, E. Corrales, J. Getty, C. Keasler, M. Mitani – Raytheon Vision Systems
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Project Overview
• HgCdTe detector cost can be reduced by using Si substrate instead of CZT • Project will develop low cost infrared detectors for astronomy with long term goal of
producing larger arrays enabled by using larger Si wafer• Project goal is to fabricate 2K x 2K MBE HgCdTe/Si detectors with competitive performance• Work is being funded by NSF and NASA to develop large format HgCdTe/Si detectors in
collaboration with Raytheon Vision Systems (RVS)
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Device Design Drivers
• Dark current and quantum efficiency identified as drivers for HgCdTe/Si design improvements
• Multiple pixel designs need to be tested• Large amount of testing required to select optimal design
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Variable Unit Cell (VUC) Devices
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4 1K x 1K variable unit cell detector die
• 1K x 1K die fabricated with 4 unit cell designs
• Design allows direct comparison of detector characteristics
• VUC detector speeds design selection and allows more time for optimization
Detectors To Date
• CfD received 4 detectors from RVS:– SN: 9A, 14, V1, and V2
• All bonded to Virgo ROICs• Current progress:
– Characterization of 2K x 2K HgCdTe/Si (SN: 14)– Characterization of 1K x 1K HgCdTe/Si (SN: V1)
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Detector Format Cutt-off (µm) substrateVirgo-9A 2K x 2K 1.7 CZTVirgo-14 2K x 2K 4.9 SiVirgo-V1 1K x 1K 2.5 SiVirgo-V2 1K x 1K 2.5 SiV1 and V2 are Variable Unit Cell (VUC) devices
None are substrate removed devices
Rochester Imaging Detector Laboratory (RIDL) in The Center for Detectors (CfD)
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• 3 cryogenic test systems• Computing cluster for data acquisition and reduction
running automated test suite• Test systems integrate with telescope for on-sky
evaluation of detectors• Test systems have been designed and used for
radiation testing
Test Results for an Array-Based GM_APD Detector Before and After Irradiation
K. Kolb’s Poster L10
Detector Control Electronics
9Potentiometer
SMT JFETThrough Hole
JFET
SMT resistor
J 1
J 2 N 4 3 9 3
0
V 1
1 6 . 5
R 16 . 5 k
M 1
M b re a k p
0
V 2TD = 0
TF = 1 0 nP W = 4 . 9 9 uP E R = 1 0 u
V 1 = 1 . 2
TR = 1 0 n
V 2 = 2 . 2
0
V 3
2 . 0
J 2
J 2 N 4 3 9 3
R 26 . 5 k
M 2
M b re a k p
0
0
V 5
2 . 0
V 6
1 . 7
R 31 0C 1
0 . 1 u
0
C 20 . 1 u
0
I
V V
I
ARC Gen III controller used to operate the detectors
• Mezzanine current source board designed for output buffer current supply
• ~7e- CDS noise - includes cabling• Noise not increased significantly with addition
of current source circuit
Virgo-14 Read Noise
• 18 e- read noise CDS• 5.5 e- read noise Fowler-16• Noise may be improved with bias noise reduction
Detector Format Cutt-off (µm) substrateVirgo-9A 2K x 2K 1.7 CZTVirgo-14 2K x 2K 4.9 SiVirgo-V1 1K x 1K 2.5 SiVirgo-V2 1K x 1K 2.5 SiV1 and V2 are Variable Unit Cell (VUC) devices
None are substrate removed devices
Virgo-14 Well Depth, Non-linearity, and Gain
• Well depth: 126 K e-
• Non-linearity terms: – a = 1.712E-6– b = -1.59E-11
21 bDNaDNcountRate
ext. gain int. gain MUX gain conv. gain conv. gain C cell
m V/ADU m V/ADU gain e-/ADU m V/e
-fF
5.9 11.69 13.23 0.88 2.50 5.29 30.2325.1 3.26 3.66 0.89 0.63 5.81 27.54
GainVIRGO-14
ARC
Virgo-14 Crosstalk
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• Crosstalk measured using cosmic rays in dark exposures• 3 x 3 grid shows crosstalk in nearest neighbors around central hit• Results given in percentage of hit signal
0.15 1.52 0.13
1.61 100.00 1.63
0.15 1.50 0.15
Number of Events: 1295
Crosstalk Results (%):
Detector Temp. (K): 37.0
Number of images: 6
H2RG-015-5.0µm
0.00 0.53 0.01
0.77 100.00 0.75
0.00 0.50 0.02
Detector Temp. (K): 30.0
Number of images: 2
Number of Events: 304
Crosstalk Results (%):
SB304-008-5.0µmVIRGO-14-4.9µm
Asymmetric crosstalk due to incomplete settling
Virgo-14 Dark Current
• Virgo-14 produced for a previous RVS project• Device being used as benchmark to compare future devices against• Currently measuring QE and validating 4.9 µm cut-off
0.01
0.10
1.00
10.00
100.00
1000.00
30 50 70 90 110 130 150
Dar
k C
urr
ent
(e-/
s/p
ixel
)
Temperature (K)
Dark Current versus Temperature
VIRGO-14
.02 e-/s/pixel
Going Forward
• Project Milestones:– Characterize VUC detectors– Characterize substrate removed VUC detectors– Select pixel design using VUC detector performance– Fabricate and characterize 2K x 2K substrate removed
MBE HgCdTe/Si device • Long term goals for MBE HgCdTe/Si process:
– Scale design to 4K x 4K and 8K x 8K– Reduce pixel pitch
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CfD Personnel
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P.I.
Don Figer
BS, ME
Kenneth Bean
Brandon Hanold
Engineer
Joong Lee
Engineer Engineer
Iain Marcuson
Matt Davis
MS, EE
PhD, IS
Kim Kolb
Mike Shaw
BS, EETBS, EE
Zach Mink
BS, Physics
Mike Every
MS, EE
Jon Zimmermann