Interacting quasi-band model for electronic states in alloy semiconductors: Relation to average t-matrix approximation and band anticrossing model

Abstract

A new variational theory is proposed for electronic states in alloy semiconductors with arbitrary diagonal and off-diagonal randomness and any concentration. In AcABcB substitutional alloys, the theory derives the mutual interaction between two quasi-A and -B electronic bands whose effective band widths are proportional to cA and cB, respectively, i.e., an interacting quasi-band model. The model provides satisfactory results near-band-edge states, especially for band bowing. For diagonal randomness, the theory corresponds to the average t-matrix approximation, and in the dilute limit, a formula similar to the band anticrossing model, which has been frequently applied to GaN-related alloys, is obtained.