3-ELEMENT STRESSED GE-GA PHOTOCONDUCTOR ARRAY FOR THE INFRARED TELESCOPE IN SPACE

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 (approximately 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 approximately 180-mu-m. Responsivity was approximately 100 A/W, and the product of quantum efficiency and photoconductive gain, eta-G, was approximately 1 with a chopping frequency of 2 Hz. The noise equivalent power was < 5 x 10(-18) W/Hz1/2 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 eta-G had a time constant tau(c) that was proportional to N(ph)-1/2.