Percolation-controlled conduction in chalcogenide glass semiconductors

Abstract

The applicability of effective-medium percolation theory (EMPT) to the composition dependence of the electrical conductivity is discussed for binary and multicomponent chalcogenide glasses. Calculations assuming a mixture of atoms, which are applied to explain the experiment for As-Te films by Ast, do not agree with experiments on all the systems considered. By assuming a chemical which forms microscopic molecular species, the conductivity over the measured compositional range can be well described with EMPT in the As-Se, As-S, and ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$-${\mathrm{Sb}}_{2}$${\mathrm{Se}}_{3}$ systems, except for Te-Se, ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$-${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$, and ${\mathrm{As}}_{2}$${\mathrm{S}}_{2.63}$-Te which contain the isomorphous Te, Se, and S atoms. Chalcogenide glasses can be classified roughly into three groups: a random mixture of atoms type, a strong chemical ordering type, and an isomorphous-atom type. It is suggested that EMPT has broad application in structural studies of chalcogenide glasses.