CATION DEPENDENCE OF THE ELECTRONIC-STRUCTURE OF ALAS AND GAAS

Effects of the cation potential on the electronic structure of AlAs and GaAs are studied using the ab initio pseudo-potential method. Differences between the band gaps and one-electron levels of AlAs and GaAs are explained in terms of the s, p and d angular components of the Al and Ga potentials. Substituting the s- and d-channels of Ga for the corresponding channels in the Al potential reduces the AlAs direct gap by 0.7 and 0.5 eV, respectively. A reduction in the ionicity of GaAs compared to AlAs is mostly due to the stronger Ga-s potential. Comparisons are made to a previous analysis of cation effects in the III-V nitrides.