Theory of alloy broadening of deep electronic energy levels in ternary semiconductor alloys

Abstract

The effects of alloy disorder on deep electronic levels produced by point defects in some of the technologically important ternary semiconductor alloys are investigated using the embedded cluster method and the theory of deep levels. Deep levels produced by defects both with nearest-neighbor and with second-neighbor alloy disorder are studied. The alloy host is treated by embedding an ensemble of clusters each of which contains five atoms (for nearest-neighbor disorder) or seventeen atoms (for second-neighbor disorder) in a virtual crystal approximation effective medium. The theory of deep levels is then used to find the deep levels in the bandgap of the host material for each cluster configuration when the central atom is replaced by a point defect. Results are presented for the inhomogenously broadened deep level spectra due to substitutional impurities on the anion site in AlxGa-x.As, Hg1-xCdxTe, and GaAS1-x, Px as well as due to the ideal As vacancy in AlxGa1-xAs. Specifically, the alloy composition dependences of the first moment, the component deep levels, and the linewidths of the spectra associated with these defects are presented.