Design of the stressed Ge:Ga far-infrared array for SIRTF

Stressed Ge:Ga is currently the most suitable detector type for very low background operation in the 115 to 200 micrometers range. Nonetheless, substantial advances have been required to develop stressed Ge:Ga detectors that work at the background limit in SIRTF. Both dark current and read noise have been improved significantly for the SIRTF devices. The design also takes account of space flight requirements such as the necessity to anneal the focal plane thermally using a minimum of cryogenic power dissipation, and the desire that any failures not propagate through an entire focal plane. The SIRTF 2 X 20 pixel focal plane will have dark current of about 200 e/s, read noise of 100 e rms, and responsivity > 7 A/W. As a result, even in the darkest parts of the sky, it will reach the background limit in less than 4 seconds of integration.