Effects of cation d states on the structural and electronic properties of III-nitride and II-oxide wide-band-gap semiconductors

Using first-principles methods based on density functional theory within the local density approximation (LDA) we calculate the structural and electronic properties of wurtzite MgO, ZnO, and CdO, and discuss their similarities and dissimilarities with the corresponding Group-III nitrides AlN, GaN, and InN. We treat the semicore d states of Zn, Cd, Ga, and In explicitly as valence states in a pseudopotential approach, investigate the effects of including on-site Coulomb interaction for Zn, Cd, Ga, and In semicore d states within the LDA+U method, and propose a novel approach to calculate the parameter U. Our results show that the LDA+U approach systematically improves the LDA band gap by indirectly acting on both the valence-band maximum and conduction-band minimum. We also discuss the effects of the on-site Coulomb interaction on structural parameters and absolute deformation potentials of ZnO, CdO, GaN, and InN.