Structural and Electronic Properties of Corundum and Monoclinic (Al1-xInx)2O3 Alloys by First-Principles

Ga₂O₃ ultrawide bandgap semiconductors have garnered significant attention in recent years due to their ultra-wide bandgap. In this study, the alternative III-oxide material using indium and aluminum mixing to form (Al_1-xIn_x)₂O₃ alloy (AlInO) is systematically investigated using hybrid density functional theory calculations. The lattice constants, bandgaps and bowing parameter are investigated for both corundum and monoclinic AlInO, with In-content ranging from 0 to 100%. A notable decrease in the bandgap energy of Al₂O₃ is observed with the increase of In content, providing a wide bandgap energy tuning range of 5.59 eV (corundum)/4.79 eV (monoclinic). In addition, results of band alignment present both type-I/type-II band offset in AlInO/β-Ga₂O₃ structure among the entire composition range. The bandgap energy of AlInO ranges from 7.93 to 2.77 eV for monoclinic AlInO, and 7.89 to 2.84 eV for corundum AlInO, in which the conduction band position exhibits a sharp upward and becomes dominant in bandgap tuning. Overall, the work indicated that AlInO alloys can potentially serve as lattice-matched materials with β-Ga₂O₃ for the electronic and optoelectronic applications, with promising surface and interface characteristics that merit further exploration.