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Ga₂O₃ is a wide-bandgap semiconductor with promising applications in high-power devices and UV photodetectors. It occurs in several polymorphs, with monoclinic β-gallia as the thermodynamically stable phase. Other polymorphs of Ga₂O₃ can be stabilized as well, but are less studied. The κ-polymorph is of interest, as it possesses ferroelectric properties and exhibits large spontaneous electrical polarizations.
Here we use density functional theory with hybrid functionals to elucidate how alloying with Al₂O₃ and In₂O₃ can be used to modify the structural and electronic properties. We focus on how the lattice constants and bandgaps can be tuned as a function of Al/In concentration. Our results show that the lattice constants vary linearly following Vegard’s law. The bandgap changes nonlinearly, with the Al alloys exhibiting a larger bandgap bowing [1]. We also report the absolute alignments of valence and conduction bands. These results can be used to guide the experimental design of new devices.

[1] S. Seacat, J.L. Lyons, and H. Peelaers. Appl. Phys. Lett. 116, 232102 (2020)