Optical absorption in degenerate semiconductors

Abstract

The optical absorption in doped direct gap semiconductors in which the conduction band may be considered as a degenerate Fermi system is studied near the Burstein edge. The problem is treated within a simple model by the methods of perturbation theory taking into account the final-state interaction between conduction electrons and the deep hole created by the photon. Particular attention is paid to Auger processes which play a fundamental role in the determination of the absorption spectrum. It is shown in detail how one passes continuously from the usual Auger broadened Burstein edge to the resonant spectrum characteristic of an infinitely heavy hole. In any case, an exciton line, distinct from the threshold, never exists