Tight-binding studies of the electronic band structure of GaAlN and GaInN alloys

Abstract

The semi-empirical tight-binding (TB) approach with an sp3s* orbital basis is used to investigate the electronic band structure of cubic Ga1-xAlxN and Ga1-xInxN alloys. The spin–orbit splitting in the Hamiltonian and first- and second-neighbour interactions are considered to explore the gap evolution as a function of the concentration x. The TB parameters used in the studies were obtained within the virtual crystal approximation using those of the binary compounds AlN, GaN, and InN. The binary parameters are calculated by applying an empirical TB Hamiltonian taking into account first- and second-neighbour interactions. A direct to indirect gap transition is obtained for Ga1-xAlxN at x=0.60. In contrast, the Ga1-xInxN alloys exhibit direct-gap characteristics as a consequence of being formed by the direct-gap binary compounds GaN and InN.