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Proceedings Paper

Visible to SWIR response of HgCdTe HDVIP detectors
Author(s): A. I. D'Souza; E. W. Robinson; M. G. Stapelbroek; W. Wong; M. Skokan; H.-D. Shih
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Paper Abstract

Detectors that have broadband response from the visible (~ 400 nm) to near infrared (~ 2.5 μm) have remote sensing hyperspectral applications on a single chip. 2.2 and 2.5 μm cutoff detectors permit operation in the 200 K range. The DRS HDVIP detector technology is a front side illuminated detector technology. Consequently, there is no substrate to absorb the visible photons as in backside-illuminated detectors and these 2.2 and 2.5-μm-cutoff detectors should be well suited to respond to visible light. However, HDVIP detectors are passivated using CdTe that absorbs the visible light photons. CdTe with a direct bandgap ~ 1.6 eV strongly absorbs photons of wavelength shorter than about 800 nm. Detectors in 320 x 6 arrays with varying thickness of CdTe passivation layers were fabricated to investigate the visible response of the 2.5-μm-cutoff detectors. The SWIR HDVIP detectors have well known high quantum efficiency (QE) in the near infrared region. Focus here was in acquiring array level data in the visible region of the spectrum. 320 x 6 FPA QE and NEI data was acquired using a 642 nm narrow band filter with 50 % points at 612 nm and 698 nm. The array QE average is ~ 70 % for the array with CdTe passivation thickness = 44.5 nm. The NEI is ~ 5 x 1010 ph/cm2/s at a flux Φ = 5.36 x 1013 ph/cm2/s. QE for an array with CdTe passivation thickness = 44.5 nm is ~ 10 % higher than an array with CdTe passivation thickness = 79.3 nm. In addition, a model that takes into account the complex optical properties of every layer in the HDVIP photodiode architecture was developed to predict the QE of the detectors in the near infrared and visible wavelength regions as a function of CdTe thickness. Measured QE as a function of wavelength is not a good match to the model QE probably due to limitations in the measured QE and knowledge of optical constants that are input into the model.

Paper Details

Date Published: 7 May 2009
PDF: 7 pages
Proc. SPIE 7298, Infrared Technology and Applications XXXV, 72981X (7 May 2009); doi: 10.1117/12.819206
Show Author Affiliations
A. I. D'Souza, DRS Sensors & Targeting Systems, Inc. (United States)
E. W. Robinson, DRS Sensors & Targeting Systems, Inc. (United States)
M. G. Stapelbroek, DRS Sensors & Targeting Systems, Inc. (United States)
W. Wong, DRS Sensors & Targeting Systems, Inc. (United States)
M. Skokan, DRS Infrared Technologies (United States)
H.-D. Shih, DRS Infrared Technologies (United States)

Published in SPIE Proceedings Vol. 7298:
Infrared Technology and Applications XXXV
Bjørn F. Andresen; Gabor F. Fulop; Paul R. Norton, Editor(s)

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