Theory of generation-recombination noise in intrinsic photoconductors

Abstract

A theory of generation-recombination (g-r) noise is presented for intrinsic photoconductors, such as Hg1−xCdxTe. It includes, for the first time, effects of both diffusion and drift of carriers into the high recombination region near the contacts and combined with Rittner’s equation for responsivity gives a correspondingly complete expression for the detectivity, D*. Additionally, it includes the effect of the spatial correlation between the probability of a density fluctuation occurring and the lifetime of the fluctuation, rather than using spatial averages. The derived expression for the g-r noise consists of a thermal component and a background component which add in quadrature. The bias field and frequency dependence of these two components are different and thus the behavior of the total g-r noise and of D* depends on their relative contributions. In particular D* increases with increasing bias field when the background contribution dominates. The results of calculations for noise voltage and D* for a X=0.21 Hg1−xCdxTe photoconductor are presented.