AlScO3 Perovskite - An ~8 eV Bandgap Oxide Predicted to Exhibit Low Small Hole Polaron Ionization Energies and p-Type Conductivity at Elevated Temperatures

We investigate electronic structure and dopability of an ultrawide bandgap (UWBG) AlScO3 perovskite, a known high-pressure and long-lived metastable oxide. From first-principles electronic structure calculations, HSE06(+G0W0), we find this material to exhibit an indirect bandgap of around 8.0 eV. Defect calculations point to cation and oxygen vacancies as the dominant intrinsic point defects limiting extrinsic doping. While acceptor behaving Al and Sc vacancies prevent n-type doping, oxygen vacancies permit the Fermi energy to reach ∼0.3 eV above the valence band maximum, rendering AlScO3 p-type dopable. Furthermore, we find that both Mg and Zn could serve as extrinsic p-type dopants. Specifically, Mg is predicted to have achievable net acceptor concentrations of ∼1017 cm-3 with ionization energy of bound small hole polarons of ∼0.49 eV and free ones below 0.1 eV. These values place AlScO3 among the UWBG oxides with lowest bound small hole polaron ionization energies, which, as we find, is likely due to large ionic dielectric constant that correlates well with low hole polaron ionization energies across various UWBG oxides.