Hopping theory of band-tail relaxation in disordered semiconductors

Abstract

Within a new theoretical approach the current and energy decay in amorphous semiconductors is studied. The relaxation of photoexcited carriers observed by transient photoconductivity experiments in amorphous silicon and chalcogenides can well be described by an algebraic power-law decay. The theoretical explanation is based on nonequilibrium hopping transport between localized states in a band tail. The theory reproduces the typical temperature dependence of the decay param- eter commonly explained within a multiple-trapping (MT) model. The observed deviations from the simple MT relation at low temperatures can be explained by the theory. Additionally, direct calculation of the energy relaxation reveals further insight into the dissipation process.