Bismuth-alloyed Ga₂O₃ as a novel p-type transparent conducting oxide

Ga₂O₃ is a wide-band-gap semiconductor that has attracted great attention for applications in power electronics and UV-blind detectors. It is easy to make it n-type by adding Si, Ge, or Sn, yet difficult (or impossible) to make it p-type unless its electronic structure is fundamentally changed. Here we show that adding a few percent of Bi to Ga₂O₃ leads to an intermediate valence band that is sufficiently high in energy to enable p-type doping. Using first-principles calculations we study the electronic structure of Bi-alloyed Ga₂O₃ and the doping efficiency of possible acceptor impurities in this system. Specifically, we discuss the results for Mg, Zn, and Cu acceptors in (Bi_xGa_1-x)₂O₃, including their most favorable incorporation sites, formation energies, and transition energy levels. We show that dilute (Bi_xGa_1-x)₂O₃ alloys could be good candidates for novel p-type transparent conducting oxide that will create new opportunities in Ga₂O₃-based device design.