Natural band alignment of MgO1−xSx alloys

We have calculated formation enthalpies, bandgaps, and natural band alignment for MgO1−xSx alloys by first-principles calculation based on density functional theory. The calculated formation enthalpies show that the MgO1−xSx alloys exhibit a large miscibility gap, and a metastable region was found to occur when the S content was below 18% or over 87%. The effect of S incorporation for bandgaps of MgO1−xSx alloys shows a large bowing parameter (b ≃ 13 eV) induced. The dependence of the band lineup of MgO1−xSx alloys on the S content by using two different methods and the change in the energy position of the valence band maximum (VBM) were larger than those of the conduction band minimum. Based on the calculated VBM positions, we predicted that MgO1−xSx with S content of 10%–18% can be surface charge transfer doped by high electron affinity materials. This work provides an example to design for p-type oxysulfide materials.