Optical properties of AlN and GaN under pressure: An ab-initio study

Theoretically calculated dielectric functions are presented for wurtzite and high pressure rocksalt phases of AlN and GaN. The spectra are calculated in a wide range of photon energies as well as in a a very narrow window near the band gap. The binding energies of excitons have been estimated. For the wurtzite phases they are: 0.105 and 0.033 eV for AlN and GaN, and for the high pressure rocksalt phases they are: 0.11 and 0.061 eV. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.