Theory of electron confinement and electron effective mass in dilute nitride alloys and heterostructures

Abstract

The band-anti-crossing (BAC) model describes the strong band-gap bowing at low N composition x in Ga(In)N x As 1-x in terms of an interaction between the conduction band edge and a higher-lying band of localized nitrogen resonant states. We first present an analytical technique based on the BAC model to calculate electron energies in Ga(In)NAs square quantum well (QW) structures. We then show through detailed comparison with photoreflectance measurements that the BAC model successfully describes ground and excited state interband transition energies in bulk and QW GaNAs samples, both at ambient pressure and as a function of hydrostatic pressure. Turning to the conduction band dispersion, we find that the twolevel BAC model is insufficient, and must be modified to give a quantitative understanding of the unexpectedly large electron effective mass values observed in some GaNAs samples, which we attribute to hybridisation between the conduction band edge and nitrogen states close to the band edge. We predict a non-monotonic variation of electron mass with hydrostatic pressure in many GaNAs samples.