Role of semicore states in the electronic structure of group-III nitrides: An exact-exchange study

Abstract

The band structure of the zinc-blende phase of AlN, GaN, and InN is calculated employing the exact-exchange (EXX) Kohn-Sham density-functional theory and a pseudopotential plane-wave approach. The cation semicore d-electrons are treated both as valence and as core states. The EXX band gaps of AlN and GaN (obtained with the Ga3d electrons included as core states) are in excellent agreement with previous EXX results, GW calculations, and experiment. Inclusion of the semicore d-electrons as valence states leads to a large reduction in the EXX band gaps of GaN and InN. Contrary to common belief, the removal of the self-interaction, by the EXX approach, does not account for the large disagreement for the position of the semicore d electrons between the LDA results and experiment. © 2005 The American Physical Society.