Alloying hexagonal/orthorhombic Ga₂O₃ with Al₂O₃

Ga₂O₃ is a wide-band-gap semiconductor with promising applications in high-power devices and UV photodetectors. It occurs in several polymorphs, with monoclinic β-gallia the thermodynamically stable phase. Other polymorphs of Ga₂O₃ can be stabilized as well, but are less studied. The ε- and κ-polymorphs are of interest as they possess ferroelectric properties and exhibit large spontaneous electrical polarizations.
Here we use density functional theory with hybrid functionals to elucidate how alloying with Al₂O₃ can be used to modify the structural and electronic properties of Ga₂O₃. We focus on tuning lattice constants and band gaps as a function of Al concentration. We also report the absolute alignments of valence and conduction bands. Our quantitative results can be used to guide experimental design of new devices.