COORDINATE DEPENDENCE OF PHOTOSENSITIVITY AND OTHER PECULARITIES OF EXTRINSIC PHOTOCONDUCTOR DETECTORS AT LOW BACKGROUNDS

The frequency dependence of the electric charge screening length in extrinsic semiconductors is analyzed. The coordinate dependence of the extrinsic photoconductor detector sensitivity on local illumination of the detector is found and it is shown that in the frequency range lying near the inverse dielectric relaxation time tau(D)-1, with local illumination of the detector domain adjacent to the injecting contact the photoconductive pin is equal to 2G0, whereas with uniform illumination of the detector it is equal to G0 = (tau/tau(d)) > 1, where tau(d) is the time to drift between contacts. It is found that photocurrent fall-off frequency can significantly exceed tau(D)-1, and the fall-off frequency of the high frequency plateau of the photocurrent characterized by a photoconductive pin of 1/2 is equal to 2/tau(d).