Investigation of p-Type Doping in β-and κ-Ga₂O₃

We have systematically investigated the effects of all possible combinations of vacancies and silicon substitutions on the electronic structure of the β and κ phases of Ga₂O₃ using plane-wave density functional theory (DFT) methods. It was found that V_Ga defects are associated with a sufficient shift of the Fermi level to lower energy to induce p-type behavior, with formation energies in the range of 9.0 ± 0.2 eV. Calculations with single atom substitutions in the κ phase, including nitrogen, phosphorous, and silicon, did not show p-type character, although N_O substitutions may lead to shallow acceptor states. In the pursuit of elucidating how MOCVD growth of Ga₂O₃ can result in p-type behavior, as indicated by experimental results in the literature, we examined the role of combining hydrogen and silicon substitutions. The results showed that p-type behavior is observable when gallium atoms are substituted for hydrogen within the coordination sphere of Si_O substitutions. This shows that silicon can act as an amphoteric dopant for p-type Ga₂O₃ semiconducting materials when hydrogen is included with formation energies < 6.0 eV.