Ab initio study of anomalous band-gap bowing in GaAs1-xNx alloys

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 GaAs1-xNx 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 stares descend into the fundamental gap, filling it ei:her partially or completely. The band gap for the random alloys also shows an anomalous bowing.