Structure and gap of low-$x$ (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloys

TL;DR

This study uses density functional theory to analyze how indium substitution affects the structure and electronic properties of Ga$_2$O$_3$, revealing limits on In incorporation and the impact on band gap due to volume changes.

Contribution

It provides new insights into the structural energetics and maximum indium content in (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloys, highlighting the role of chemical pressure.

Findings

Maximum In content is limited to 12-25% due to structural energetics.

Band gap variation is mainly driven by volume changes with doping.

Most In sites are energetically inaccessible for substitution.

Abstract

We study the electronic and local structural properties of pure and In-substituted $\beta$-Ga$_2$O$_3$ using density functional theory (DFT). Our main result is that the structural energetics of In in Ga$_2$O$_3$ causes most sites to be essentially inaccessible to In substitution, thus reducing the maximum In content in thi to somewhere between 12 and 25 \% in this phase. We also find that the gap variation with doping is essentially due to "chemical pressure", i.e. volume variations with doping.