A theory of a.c. conduction in chalcogenide glasses

Abstract

An electrical conductivity having a frequency dependence ∼ω ^s , where s < 1, has been reported for many amorphous semiconductors and chalcogenide glasses. It is the purpose of this paper to point out that the mechanism normally postulated for this behaviour, namely, thermally assisted quantum-mechanical tunnelling, is inappropriate for the case of the chalcogenide glasses. Instead, a mechanism is proposed in which two electrons hop over a potential barrier between defect sites, the height of the barrier being correlated with the intersite separation. The theory of this effect is seen to explain many features observed experimentally; in particular, the variation of the exponent a between different materials and its temperature dependence. New estimates for the spatial densities of states of these materials are made and are in reasonably close agreement with values inferred from other experimental data.