Optical Properties of Acceptor Impurities in Ga₂O₃

Ga₂O₃ has attracted great attention as a promising material for high power electronic applications due to a very large band gap, high breakdown voltage and ability to be doped n-type. The Ga₂O₃ Baliga’s figure of merit is only lower than that of diamond. Most importantly, large single crystals of Ga₂O₃ are available, facilitating epitaxial growth. Although p-type Ga₂O₃ have not been demonstrated as acceptor impurities tend to introduce deep acceptor levels, they can be used to make semi-insulating layers, and that can be useful in device designing. The deep levels of acceptor impurities in ultra-wide-band gap oxides are often difficult to probe experimentally. To facilitate the experimental characterization of the acceptor impurities, we employed hybrid density-functional calculations to investigate the optical transitions of acceptor impurities in monoclinic Ga₂O₃. We constructed configuration coordinate diagrams to determine the absorption and emission energies that can be compared with the optical absorption and photoluminescence measurements. The results show that all impurities exhibit deep acceptor transitions. The calculated emission energies are compared with the available experiment data.