Predicted energy band gaps of (AIIIBV)1-xX2xIV metastable, substitutional, crystalline alloys.

Abstract

Predictions of the energy band gaps as functions of alloy composition are given for the Greene alloys, which are metastable, crystalline, substitutional alloys of III-V compounds and group-IV elemental materials. All possible combinations of these alloys involving Al, Ga, In, P, As, Sb, Si, Ge, and Sn are considered. The \ensuremath{\Gamma} and L conduction-band minima, relative to the valence-band maxima, exhibit characteristic V-shaped bowing and kinks as functions of composition x; the band edges at point X bifurcate at critical compositions corresponding to the order-disorder transition of Newman et al. The V-shaped bowing due to the transition offers the possibility of band gaps significantly smaller than expected on the basis of the conventional virtual-crystal approximation. Alloys with modest lattice mismatches that are predicted to have especially interesting band gaps include (InP${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{2\mathrm{x}}$, (AlSb${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sn}}_{2\mathrm{x}}$, (GaSb${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sn}}_{2\mathrm{x}}$, and (InAs${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sn}}_{2\mathrm{x}}$, which are alloys with potentially small band gaps, and (AlAs${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{2\mathrm{x}}$ and (GaAs${)}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Si}}_{2\mathrm{x}}$, which are alloys with larger gaps and several interesting band-edge crossings as functions of composition.