Gain Saturation in Extrinsic Germanium Photoconductors Operating at Low Temperatures

Abstract

A semiempirical model has been developed for the frequency dependence of the photoconductive response of high‐resistivity extrinsic Ge samples operating at cryogenic temperatures. The model predicts that the photoconductive gain saturates to the sweepout‐limited value of ½ for frequencies greater than G(0)/πτ_ρ, where G(0) is the dc photoconductive gain and τ_ρ=εε₀ρ is the dielectric relaxation time. Measurements of signal as a function of modulation frequency and background for a large Ge : Hg sample at liquid neon (∼ 28°K) show good agreement with the model.