The mechanism for a.c. conduction in chalcogenide semiconductors: Electronic or atomic?

Abstract

The effect of pronounced pairing of oppositely charged defect centres on a.c. conduction in chalcogenide glasses is discussed. It is concluded that for this non-random case, the conductivity should be fairly accurately linear with no temperature dependence for some typical chalcogenide glasses. However, for certain combinations of bandgap and glass-transition temperature, a superlinear frequency dependence may occur. Conversely, a random distribution of centres gives rise to an a.c. conductivity that is sublinearly frequency dependent and also temperature dependent. The fundamental mechanism for a.c. conduction is assumed to be the same in both cases: the simultaneous hopping of two electrons between two oppositely charged sites over the barrier separating them whose height is correlated with the intersite separation through the Coulomb attraction. In this way, an atomic mechanism need not be invoked in order to explain a conductivity that is linearly dependent on the frequency.