Localized Defects in Semiconductors

Abstract

A method of calculating the energies of bound states associated with imperfections described by short-range potentials in semiconductors is presented and applied. The method is based on solid-state scattering theory and involves expansion of physical quantities in terms of the Wannier functions for a many-band system. The properties of Bloch functions and Wannier functions are investigated to enable the numerical computation of matrix elements. Application is made to the neutral vacancy in silicon. A pseudopotential is employed to represent the change in the crystal potential produced by the vacancy. It is found that the vacancy produces a localized state in which low-lying energy bands and interband couplings are important, in contrast to the shallow donor and acceptor states which have been studied in the past.