The density of states for a classical impurity band

Abstract

The distribution of donor energies rho is calculated both analytically and numerically for the ground state of an array of randomly located donors and acceptors (subject only to Coulomb interactions) when the compensation ratio K is small. The analysis provides a simple form for rho in the limit K to 0. The numerical procedure generates rho from a self-averaging system of 64000 donors with K=0.01. The results are in good agreement and exhibit a deep minimum in rho near the Fermi level which is consistent with the existence of a Coulomb gap.