Prospects for n-type doping of (Al_xGa_(1-x))_2O_3 alloys

摘要

We systematically explore the properties of group-Ⅳ (C, Si, Ge, and Sn) and transition metal (Hf, Zr, and Ta) dopants substituting on the cation site in (Al_xGa_(1-x))_2O_3 (A1GO) alloys using first-principles calculations with a hybrid functional. In Ga_2O_3, each of these dopants acts as a shallow donor. In Al_2O_3, they are deep defects characterized by the formation of either DX centers or positive- U (+/0) levels. Combining our calculations of dopant charge-state transition levels with information of the AlGO alloy band structure, we estimate the critical Al composition at which each dopant transitions from being a shallow to a deep donor. We identify Si to be the most efficient dopant to achieve n-type conductivity in high Al-content AlGO alloys, acting as a shallow donor over the entire predicted stability range for AlGO solid solution alloys.