First-principles study of γ-CuI for p-type transparent conducting materials

gamma-CuI has attracted considerable attention recently as a p-type transparent conductive material. In this paper, we have investigated the hole effective mass, intrinsic defects and group VI-A impurities in gamma-CuI by first-principles calculations. We found that the hole effective mass of gamma-CuI is light, in line with the high p-type mobility observed in experiments. The p-type conductance is expected to originate from Cu vacancies, which have a low formation energy with no significant n-type compensating defects. The relative high transition level of Cu vacancy, however, may lead to a low hole concentration in the gamma-CuI sample. Additionally, no shallow transition levels were found in gamma-CuI with substitutional group VI-A impurities at I sites.