Analysis of nonohmic current-voltage characteristics in a Cu-compensated GaAs photoconductor

Abstract

An analysis of observations of nonohmic current conduction in a copper-compensated GaAs (GaAs:Cu) photoconductive switch is presented. It is demonstrated that conduction during illumination and at modest current densities can be attributed to an optically injected plasma influenced by single-injection contact effects. However, at higher current densities, a double-injection model is more suitable. We provide further evidence that the transition from a single-injection process to a double-injection process is accompanied by the formation of at least one current filament with cross-sectional area of 5×10−4 cm2, and a peak current density greater than 103 A/cm2. We finish by suggesting avalanche breakdown at the n+−i anode junction as a possible mechanism for the onset of significant hole injection at the anode, a condition necessary to justify the use of a double-injection-dominated transport model in an essentially n-i-n device.