Hot-Carrier Model for an Anomalous Exponent of Photoconduction

Abstract

Experiments often show that the photoconductance $σ$ of a semiconductor system and the light intensity $I$ are related by $σ\sim I^γ$. Conventional theories give a satisfactory explanation for $γ=1$ or $γ=1/2$, but anamalous exponents close to $γ=3/4$ are often observed. This paper argues that there is a universal anomalous regime for which $γ=3/4$ (or $γ=2/3$ in two-dimensional samples), resulting from the kinetics of electron-hole recombination being controlled by Coulombic attraction. Because the local electric fields are extremely high, the theory appeals to the 'hot-carrier' model for transport in semiconductors.

11 pages, 1 figure