Electronic and optical properties of MgxZn1−xO and CdxZn1−xO from ab initio calculations

Isostructural and heterostructural pseudobinary MgxZn1−xO and CdxZn1−xO alloys are studied by combining the wurtzite and the rocksalt polymorphs within a cluster expansion. The computationally demanding calculation of the quasiparticle electronic structure has been achieved for all cluster cells of the expansion using the recently developed HSE03 +G0W0 scheme. These results are used to compute the configurational averages for the fundamental band gaps and the densities of states. A strongly nonlinear behavior of the band gaps is observed and it is quantified by means of the corresponding bowing parameters for both material systems. In order to calculate the macroscopic dielectric functions, including excitonic and localfield effects for isoand heterostructural MgxZn1−xO alloys as well as wurtzite (wz) CdxZn1−xO, the Bethe–Salpeter equation has been solved for each of the corresponding clusters. The respective configurational averages indicate that the composition-dependent variation in the exciton peaks allows conclusions on the alloy composition and preparation conditions. 1 Author to whom any correspondence should be addressed. 2 Current address: Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. New Journal of Physics 13 (2011) 085012 1367-2630/11/085012+24$33.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft