Improved Performance Characteristics For Indium Antimonide Photovoltaic Detector Arrays Using A FET-Switched Multiplexing Technique

Abstract

Performance characteristics of indium antimonide (InSb) linear infrared (1-5 micrometer) hybrid focal plane assemblies operating in a capacitive-discharge mode (CDM) which use a FET-switched multiplexer are discussed. Specific improvements in each of the two major components of these assemblies have demonstrated increased feasibility for use in high background environments. It is the objective of this paper to detail these improvements and discuss certain additional performance parameters. Previous papers dealt specifically with low background applications using this technique. Emphasis is therefore placed on the characteristics considered significant to the high background, tactical environment. Recent testing of hybrid assemblies using a newly modified Reticon FET-switched multiplexer chip indicate several distinct improvements over the previous version. These include a signal transfer function increase of 25%, a pixel readout rate exceeding 1 megahertz, and a reduction of the kTC component of read noise. The latter resulted in a 13% decrease in the total pixel read noise. These results were accomplished by a general reduction of video line capacitance. Incorporating the detector reset function on the multiplexer chip, thus eliminating the parasitic capacitance of the external MOSFET switch, was the primary factor facilitating the improvement. In addition, a metal bias plate structure has been added to the detector array. This functions to control surface leakage current at large reverse biases. It simultaneously reduces the dark current density and its associated shot noise. This has made it possible to measure maximum integration times of 430 milliseconds at 77 K, an increase of 38% over the previous standard. Large reverse biases are Bow practical and allow extension of the usable charge storage capacity to more than 1.2x108 electrons per storage well.© (1985) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.