CALIBRATION AND PERFORMANCE OF DOPED-GE PHOTOCONDUCTORS FOR THE ISO LONG-WAVELENGTH SPECTROMETER

The Long Wavelength Spectrometer (LWS), part of the Infrared Space Obs ervatory (ISO), uses an array of 10 doped-germanium photoconductors to cover the wavelength range 45 180 mum. The array comprises one Ge:Be detector for the 45-50 mum range, five unstressed Ge: Ga detectors for wavelengths between 50 and 110 mum and four stressed Ge:Ga detectors for the long wavelength range 110-180 mum. We have calibrated the perf ormance of the detectors, both individually and in the LWS. Optimum va lues of detector bias and operating temperature that maximize the sens itivity of the LWS have been established, resulting in detector NEPs r anging from 10(-17) W Hz-1/2 for Ge: Be to 5 x 10(-19) W Hz-1/2 for st ressed Ge:Ga. Under the low flux conditions expected in the LWS (< 10( -14) W at the detector), doped-Ge photoconductors exhibit a number of other non-linearities and memory effects. The characteristics of these effects are described and the implications for operation and calibrat ion of the LWS considered.