Donor and acceptor properties in Ga₂O₃ polymorphs

An ultra-wide band gap and substrate availability make Ga₂O₃ an attractive power electronic material. But questions still remain as to how best control its electrical conductivity through impurity doping. In this work, we evaluate the properties of acceptor and donor dopants in Ga₂O₃ polymorphs using first-principles calculations based on hybrid density functional theory. Hole localization and low-lying valence bands are exhibited by all Ga₂O₃ phases, causing deep acceptor behavior for all impurities considered. These polymorphs also share other properties, such as similar positions of the deep oxygen vacancy defect levels. In contrast, cation-site donors (such as C, Si, Ge, and Sn) are found to be shallow. These donors do exhibit defect transition levels above the Ga₂O₃ conduction band minimum, which may become relevant if Ga₂O₃ is alloyed with aluminum and the band gap increases.