Absolute deformation potentials and band alignment of wurtzite ZnO, MgO, and CdO

Abstract

Using first-principles methods we calculate the absolute deformation potentials ${a}_{v}$ and ${a}_{c}$ of wurtzite ZnO, MgO, CdO, and the band offsets at $\mathrm{Mg}\mathrm{O}∕\mathrm{Zn}\mathrm{O}$ and $\mathrm{Zn}\mathrm{O}∕\mathrm{Cd}\mathrm{O}$ interfaces. We find that the absolute deformation potentials of these oxides are systematically smaller in magnitude than those of the corresponding nitrides (GaN, AlN, and InN). The $\mathrm{Mg}\mathrm{O}∕\mathrm{Zn}\mathrm{O}$ and $\mathrm{Zn}\mathrm{O}∕\mathrm{Cd}\mathrm{O}$ heterojunctions exhibit type-I band lineups, in which the narrower band gap on the right (ZnO and CdO) is contained within the wider gap on the left (MgO and ZnO). The conduction-band offsets $\ensuremath{\Delta}{E}_{c}$ at these junctions are much greater than the valence-band offsets $\ensuremath{\Delta}{E}_{v}$. We explain these results in terms of the energetic position of the anion $s$ and $p$ valence states relative to the cation $s$, $p$, and $d$ valence states.