Natural band alignment of $\rm MgO_{1-x}S_{x}$ alloys

TL;DR

This study uses first-principles calculations to analyze the band alignment, formation enthalpies, and potential doping strategies of MgO-S alloys, revealing their miscibility gaps, large band gap bowing, and suitability for surface charge transfer doping.

Contribution

The paper provides the first detailed theoretical analysis of the natural band alignment and formation properties of MgO-S alloys, suggesting their potential for p-type oxysulfide applications.

Findings

Large miscibility gap and metastable regions identified.

Significant band gap bowing parameter (~13 eV) observed.

Potential for surface charge transfer doping with high electron affinity materials.

Abstract

We have calculated formation enthalpies, band gaps, and natural band alignment for $\rm MgO_{1-x}S_{x}$ alloys by first principles calculation based on density functional theory. The calculated formation enthalpies show that the $\rm MgO_{1-x}S_{x}$ alloys exhibit a large miscibilitygap, and a metastable region was found to occur when the S content was below 18% or over 87%. Effect of S incorporation for band gaps of $\rm MgO_{1-x}S_{x}$ alloys shows large bowing parameter (b $ \simeq $ 13 eV) induced. The dependence of the band lineup of $\rm MgO_{1-x}S_{x}$ alloys on the S content by using two different methods, and the change in the energy position of valence band maximum (VBM) was larger than that of conduction band minimum. Based on the calculated VBM positions, we predicted that $\rm MgO_{1-x}S_{x}$ with S content 10 to 18% can be surface charge transfer doping by high electron affinity materials. The present work provides an example to design for p-type oxysulfide materials.