Corundum, bixbyite, and monoclinic alloys of Al₂O₃ and In₂O₃

By alloying Al₂O₃ and In₂O₃ with Ga₂O₃ [1-4], material properties such as bandgaps (for optical devices) and lattice constants (to control strain) can be tailored to the requirements of specific device applications, with several demonstrated applications. The design space can be increased by considering InAlO₃ alloys. However, a characterization and understanding the properties of InAlO₃ alloys is still missing. We therefore use density functional theory (DFT) with hybrid functionals to detail the energetics and changes in electronic and structural properties of these alloys. We consider alloys in the bixbyite, corundum, and monoclinic crystal structures. Our results show that the pseudocubic lattice constants for all structures increase linearly as a function of In content, following Vegard’s law. The bandgap decreases nonlinearly, exhibiting stronger bowing in the corundum (b=4.16 eV) and bixbyite structures (b=4.9 eV) than the monoclinic structure (b=1.73 eV). These findings can be used for rational device design.

[1] Appl. Phys. Lett. 119, 042104 (2021)

[2] Appl. Phys. Lett. 116, 232102 (2020)

[3] Appl. Phys. Lett. 112, 242101 (2018)

[4] Phys. Rev. B 92, 085206 (2015)