Properties of (Ga$_{1-x}$In$_x$)$_2$O$_3$ over the whole $x$ range

TL;DR

This study uses density-functional ab initio techniques to analyze the structural, compositional, and electronic properties of (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloys across all compositions, revealing a large, temperature-independent miscibility gap and phase behavior.

Contribution

It provides a comprehensive theoretical analysis of (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloys over the entire composition range, highlighting phase stability, miscibility gaps, and electronic property anomalies.

Findings

Large, temperature-independent miscibility gap identified.

Phase stability varies with composition and growth conditions.

Electronic offsets show notable anomalies as a function of In content.

Abstract

Using density-functional ab initio theoretical techniques, we study (Ga$_{1-x}$In$_x$)$_2$O$_3$ in both its equilibrium structures (monoclinic $\beta$ and bixbyite) and over the whole range of composition. We establish that the alloy exhibits a large and temperature-independent miscibility gap. On the low-$x$ side, the favored phase is isostructural with $\beta$-Ga$_2$O$_3$; on the high-$x$ side, it is isostructural with bixbyite In$_2$O$_3$. The miscibility gap opens between approximately 15\% and 55\% In content for the bixbyite alloy grown epitaxially on In$_2$O$_3$, and 15\% and 85\% In content for the free-standing bixbyite alloy. The gap, volume and band offsets to the parent compound also exhibit anomalies as function of $x$. Specifically, the offsets in epitaxial conditions are predominantly type-B staggered, but have opposite signs in the two end-of-range phases.