ONSET OF A NONOPTIMAL HOPPING REGIME FOR AC CONDUCTIVITY IN AMORPHOUSGALLIUM ANTIMONIDE

A possible explanation has been found for the typical discrepancy betw een the parameters of localized states as determined from the static a nd dynamic hopping conductivities in tetrahedral amorphous semiconduct ors. It is shown for the example of a-GaSb that the Mott hopping lengt h R(opt), the correlation length for nonoptimal hops L(T), and the ac hopping length R(omega) are related as R(opt) < L(T) < R(omega), as a result of which the Mott law holds for the de conductivity and the Zvy agin regime of nonoptimal hops holds for the ac conductivity sigma(ome ga). The observed value of sigma(omega) is two orders of magnitude low er than the conductivity calculated by the Austin-Mott formula for the parameters of localized states found from de measurements. A model th at quantitatively describes the static and dynamic conductivity of a-G aSb with the aid of a single set of parameters characterizing the Mill er-Abrahams resistor network is proposed. (C) 1997 American Institute of Physics.