On the Theory of Auger Recombination in Disordered Semiconductors. A Green's Function Approach

Abstract

AbstractA Green's function approach based on the density‐operator formalism is developed to calculate the lifetime of Auger recombination in disordered semiconductors, taking explicitly into account translation‐symmetry breaking and the contribution of band‐tail states. The theory is applied to disordered materials which can be described by the smooth random field model. It is shown that the classical approximation is sufficient to produce the effect of the disorder on Auger recombination processes. Then a general expression for the Auger lifetime is derived in the form of the volume and configuration average of a local lifetime. The influence of the random field is reduced to a modification of the energy conserving δ‐function and the distribution functions of non‐equilibrium carriers. The Auger lifetime or recombination rate depends on the mean square of the random potential fluctuation, Ψ1. In the case of nondegenerate semiconductors, the Auger recombination rate is exponentially enhanced with increasing Ψ1, so that an estimate of the random parameter might be possible from Auger lifetime measurements. As an example, the Auger coefficient for p‐type GaSb is evaluated for the case of the random field due to thermal fluctuations of charge carrier concentrations.