Cooperative charge disproportionation of defects in amorphous semiconductors

Abstract

Defect centers in amorphous semiconductors with three possible states of charge (+, 0, and -) can be modeled with an antiferromagnetic S = 1 Ising Hamiltonian in an external field. We have studied this model on a one-dimensional lattice with first neighbor interactions. A clear charge disproportionation is obtained as a function of temperature for a wide range of parameters. The relevance of our finding to the ESR behavior of a-As, and possibly also the photoluminescence of a-Si:H, and to field effect behavior of chalcogenide glasses is pointed out.