A model for photoconductivity in amorphous chalcogenide alloys

Abstract

A model for photoconductivity has been developed for amorphous chalcogenide alloys which is able to describe many of the properties of these materials to provide a means of estimating the characteristic parameters of localized or partially localized states. Starting with the simplest model and semiconductor statistics, additional complexities are added only as demanded by the experimental data. The model includes recombination transitions (1) from non-localized states to high densities of localized states lying within E ∗ of the mobility edges ( E ∗ ≈ 0.1–0.3 eV ), (2) between the high density of states near the upper mobility edge to that near the lower mobility edge, and (3) from these high densities of localized states near the edges to localized states near the equilibrium Fermi level. The model describes appropriately the detailed dependence of photoconductivity on excitation intensity and temperature in a way which is consistent with the dark conductivity. Examples of quantitative application of the model are given.