From band tailing to impurity-band formation and discussion of localization in doped semiconductors: A multiple-scattering approach

Klauder's best multiple-scattering approximation which allows the use of a realistic interaction potential and in which electron-electron interactions may be incorporated is shown to constitute a sound basis for the study of the electronic structure of doped semiconductors. The implementation of this formalism requires the solution of a self-consistent set of nonlinear integral equations. This has been done numerically over a large impurity-concentration range. We have thus shown that as the concentration decreases, the band tail gradually splits off from the main band, giving an impurity band. Spectral-density analysis allows one to distinguish between localized and extended states. Compensation effects have also been analyzed. Finally, our results are discussed and compared with various experiments.