QUASI-PARTICLE EXCITATIONS IN GAAS1-XNX AND ALAS1-XNX ORDERED ALLOYS

We have performed a quasiparticle study of the fundamental excitations in ordered alloys of III-V semiconductors, GaAs1-xNx and AlAs1-xNx. The experimentally observed anomalous redshift in GaAs1-xNx of the direct band edge is explained here by effects arising from the 20% lattice mismatch. The fact that the bottom of the conduction band is mainly dominated by nitrogen leads to a large reduction of the fundamental gap at Γ as the volume increases. This reduction continues until the charge density begins to locate on the arsenic site. Based on this simple scenario, we predict that a similar redshift may be observed in the indirect gap AlAs1-xNx alloys. Also an indirect to direct band-gap transition will be observed for intermediate N concentrations. The possibility of closing the band gap is discussed in terms of the quasiparticle results. © 1995 The American Physical Society.