The impurity density-of-states tails in neutral semiconductors: application to the diffusion current in GaSb p-n junctions

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Abstract
A simplified approach of the Halperin and Lax model of the density-of-states tails in heavily doped semiconductors is presented: the trial wavefunctions are assumed to be hydrogen-like ones. Analytical expressions of the density-of-states tails are obtained, in very good agreement with the computed Halperin and Lax results. The connection of the density-of-states tail with the unperturbed parabolic band is then achieved in the same way as previously done by Hwang, and numerical values are calculated for various doping levels in GaSb. The influence of the band tails on the electrical I-V characteristic, and on the optical luminescence spectra, is calculated. Good agreement is shown with experimental results on GaSb p-n junctions. Thus valuable information about the location and spectral properties of the recombinations in p-n junctions can be deduced from this simplified band-tail model.