<i>Ab initio</i>study of anomalous band-gap bowing in alloys

Abstract

A full potential self-consistent linear muffin-tin orbital method in the local density approximation (LDA) has been employed to investigate the electronic structure of the 14 ordered alloys with x = 0.0, 0.037, 0.074, 0.111, 0.125, 0.25, 0.375, 0.407, 0.50, 0.625, 0.75, 0.875, 0.963 and 1.0. The lattice parameter is seen to have a non-linear variation with the concentration of the constituent atoms. In LDA, a near closure of the fundamental energy gap appears in the concentration range 12.5-62.5% of N atoms. A strong hybridization of N s states with the Ga (s, p) and As (s, p) states is seen at the bottom of the conduction band and these states descend into the fundamental gap, filling it either partially or completely. The band gap for the random alloys also shows an anomalous bowing.