Using density-functional ab initio theoretical techniques, we study
(Ga1−x​Inx​)2​O3​ in both its equilibrium structures (monoclinic
β 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 β-Ga2​O3​;
on the high-x side, it is isostructural with bixbyite In2​O3​. The
miscibility gap opens between approximately 15\% and 55\% In content for the
bixbyite alloy grown epitaxially on In2​O3​, 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.Comment: 7 pages, 4 figure