Two band model of a disordered semiconducting binary alloy in the coherent potential approximation

Formalism of the coherent potential approximation is extended to include the two band case. Single site energy of the one band case is replaced by a 2 × 2 matrix which varies randomly from site to site according to the occupancy of the site. Cases treated explicitly correspond to fully disordered binary alloys. Band gap and band widths are chosen as representative of typical semiconductor values. Concentrations, band gaps, gap centers, and band mixing are all varied systematically. Results are exhibited for the total densities of states and their parentage. Various limits of splitband and gap closure are shown by phase diagrams.