Transient photocurrent due to step-function excitation in disordered materials-computer simulation and analytical treatment

Abstract

The problem of the transient photoconductivity induced in a disordered dielectric sample by step-function excitation is treated in detail under the quasi-neutrality approximation. The carrier generation is assumed to be uniform. Unipolar (for example, hole) conduction is considered so that mobile holes recombine with localised electrons. Before recombination, a hole can be captured by localised states (traps) with release time controlled by the activation energies of traps and the temperature. There exists a broad spectrum of activation energies in disordered materials. In this paper the authors consider an exponential model of trap energy distribution. Numerical calculations of transient photocurrent curves as well as analytical asymptotic solutions are presented. The photocurrent is shown to pass through a maximum before attaining a steady-state value.