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

1

Outline

• Project overview• Device design• Test setup• Characterization results• Going forward

2

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)

3

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

4

Variable Unit Cell (VUC) Devices

5

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)

6

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)

7

• 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

Cryostat Detail

8

Detector EnclosureCold Plate

Filter Wheel

Outer Case

Electrical Connectors

Detector Control Electronics

9Potentiometer

SMT JFETThrough Hole

JFET

SMT resistor

J 1

J 2 N 4 39 3

0

V 1

16 . 5

R 16 .5 k

M 1

M b rea k p

0

V 2TD = 0

TF = 1 0 nP W = 4 . 99 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 43 9 3

R 26 . 5 k

M 2

M b re ak p

0

0

V 5

2 . 0

V 6

1 . 7

R 310C 1

0 . 1u

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 - fF5.9 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

12

• 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: 1295Crosstalk Results (%):

Detector Temp. (K): 37.0Number 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): 30.0Number of images: 2Number of Events: 304Crosstalk 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

urre

nt (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

14

CfD Personnel

15

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

Thank you for your attention.

Questions?

16