Three-element stressed Ge:Ga photoconductor array for the infrared telescope in space

Abstract

A stressed Ge:Ga photoconductor array with three elements applied to the Infrared Telescope in Space satellite was fabricated and tested in experiments at 2.0 K in very low-photon-influx conditions (~ 10(5) photons/s). Stress was applied to three Ge:Ga detectors in a series by a stable and compact stressing apparatus by using cone-disk springs. The cutoff wavelength was ~ 180 microm. Responsivity was ~ 100 A/W, and the product of quantum efficiency and photoconductive gain, etaG, was ~ 1 with a chopping frequency of 2 Hz. The noise equivalent power was <5 x 10(-18) W/Hz((1/2)) when low-noise transimpedance amplifiers were used. A slow transient response and a nonlinear response that was dependent on the background photon influx were observed in the experiments. The latter showed that the etaG had a time constant tau(c) that was proportional to N(ph)(-(1/2)).