Band structures and optical spectra of InN polymorphs:: Influence of quasiparticle and excitonic effects -: art. no. 205106

We present ab initio calculations of the electronic structure and the optical properties of InN crystallizing in wurtzite, zinc-blende, and rocksalt structures. They are based on well converged atomic geometries including the effect of the In 4d electrons. The quasiparticle aspect is described in the framework of a GW approximation. The opposite influence of quasiparticle effects and the pd repulsion is demonstrated for the band structures. The pecularities of the band structures such as the small gap of the 2H and 3C polymorphs and their large electron affinity are discussed. The frequency dependence of the dielectric functions is explained in terms of nonparabolic bands and high-energy optical transitions at critical points. Excitonic effects drastically influence the optical absorption by an overall redshift of the entire spectrum and a redistribution of oscillator strengths. The results are critically discussed in the light of recent experiments.