QUASI-PARTICLE BAND STRUCTURES OF SHORT-PERIOD SUPERLATTICES AND ORDERED ALLOYS OF ALN AND GAN

Quasiparticle band structures of short-period superlattices and ordered alloys of AlN and GaN are calculated using the GW approximation. The calculated gaps range from 3.1 to 5.8 eV. Two types of structural materials are studied: zinc-blende superlattices in the (111) direction and hexagonal wurtzite superlattices and ordered alloys in the (001) direction. Comparisons between band structures of these materials using folding of Brillouin zone points and the transition from an indirect to direct gap semiconductor in the zinc-blende compounds are discussed. All of the wurtzite structures studied are found to have direct band gaps with values between 3.5 and 5.8 eV. The 1 x 1 and 1 x 2 AlN/GaN zinc-blende superlattices have direct gaps of 4.4 and 4.3 eV, respectively, whereas the 2 x 1 AlN/GaN superlattice gap is 4.6 eV and is indirect. Several fundamental gaps are predicted and remain to be tested by experiment.