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Proceedings Paper

Critical look at AlGaAs/GaAs multiple-quantum-well infrared detectors for thermal imaging applications
Author(s): Frank W. Adams; K. F. Cuff; George Gal; Alex Harwit; Raymond L. Whitney
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Paper Abstract

In the last five years, photoconductive infrared detectors using intersubband transitions in AlGaAs/GaAs multiple-quantum-well structures have attained more than adequate single-pixel detectivity for thermal imaging. Because AlGaAs/GaAs materials technology can potentially deliver a high yield of extremely uniform large-area detector arrays, lower-cost LWIR thermal imagers may indeed be possible. In this paper, we ask whether arrays of these detectors are suitable for staring LWIR thermal imagers. At first look they do not appear particularly attractive because of excessive dark-current pattern noise. For practical operating temperatures above 68 K (approximately the lowest temperature for single-stage cryocoolers), total dark- current variation must be reduced by more than an order of magnitude to attain a practical noise-equivalent temperature difference (NETD). Reducing dark current is therefore the most effective way to improve staring array performance. Several other measures can also improve NETD. Optimizing bias voltage for minimum NETD rather than for maximum detectivity can improve NETD by a factor of 2. Integrated micro-optics can reduce detector area, reducing pattern noise by reducing dark current. A multiple-quantum-well chopper can be used to improve correction for dark-current nonuniformity. We conclude that a practical thermal imager can probably be made with AlGaAs/GaAs MQW technology, but success will require careful modeling of all relevant factors.

Paper Details

Date Published: 1 November 1991
PDF: 14 pages
Proc. SPIE 1541, Infrared Sensors: Detectors, Electronics, and Signal Processing, (1 November 1991); doi: 10.1117/12.49316
Show Author Affiliations
Frank W. Adams, Lockheed Palo Alto Research Lab. (United States)
K. F. Cuff, Lockheed Palo Alto Research Lab. (United States)
George Gal, Lockheed Palo Alto Research Lab. (United States)
Alex Harwit, Lockheed Palo Alto Research Lab. (United States)
Raymond L. Whitney, Lockheed Palo Alto Research Lab. (United States)

Published in SPIE Proceedings Vol. 1541:
Infrared Sensors: Detectors, Electronics, and Signal Processing
T. S. Jay Jayadev, Editor(s)

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