Alloys of orthorhombic Ga₂O_3,Al₂O_{3 ,}and In₂O₃

Ga₂O₃ is a wide-bandgap semiconductor with promising applications in high-power devices and UV photodetectors. Monoclinic β-gallia is its thermodynamically stable phase, but other polymorphs can be stabilized. Of particular interest is the orthorhombic κ-polymorph, as it possesses ferroelectric properties and exhibits large spontaneous electrical polarizations.

Here we use density functional theory with hybrid functionals to elucidate how alloying Ga₂O₃ 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 [1, 2] show that the lattice constants vary linearly following Vegard’s law. The bandgap changes nonlinearly, with the Al alloys exhibiting a larger bandgap bowing. The absolute positions of the valence and conduction band edges, important for heterostructures, are also discussed. Finally, we will elucidate the properties of alloys of orthorhombic In₂O₃ and Al₂O₃, which can be used to increase the design space of heterostructures. These results can be used to guide experimental design of new devices.

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

[2] S. Seacat, H. Peelaers, and J.L. Lyons. Appl. Phys. Lett. 119, 042104 (2021).