EFFECT OF INPLANE BIAXIAL STRAINS ON THE BAND-STRUCTURE OF WURTZITE GAN

The effect of strain on wurtzite GaN is studied theoretically using an sp(3)d(5)-sp(3) empirical tight-binding model. The model incorporates all nearest-neighbor and some second-nearest-neighbor interactions wi thin the two-center approximation. The second-nearest-neighbor interac tions excluded are the cation-cation interactions involving the Ga 3d orbital. Strain is included by scaling the two-center integrals approp riately. Thus the strain is modeled without invoking deformation poten tial theory, obviating the need for any additional parameters. The pre sent model can accommodate any arbitrary strain orientation. The band structure has been calculated for in-plane biaxial strain. It is found that the band gap remains direct for in-plane biaxial strains ranging between +/- 5%. Furthermore, the valence-band edge is of a different symmetry for tensile and compressive strains. The total density of sta tes calculated via a fundamental numerical scheme is given for unstrai ned and strained GaN.