Theoretical study on the electronic and electrical properties of p-type transparent conducting metal oxides

Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate applications. In addition to good quality n-type TCOs, there is increasing demand for good p-type TCOs. In the present study, we reported a theoretical study on the electronic and electrical properties for p-type TCO, Zn-doped In₂O₃ (IZO). The geometries of IZO were optimized using the density functional theory (DFT). Based on these optimized structures, the density of states, frontier molecular orbital contours, and electrical conductivity of IZO were calculated by combining the tight-binding quantum chemical molecular dynamics program, "Colors" and Monte Carlo method. The calculated band gap by "Colors" at G point is 2.87 eV, which is in good agreement with experimental value. In density of states of IZO, a shallow acceptor-type impurity level associate with Zn doping was observed above the top of the valence band. The frontier orbital analysis shows that the acceptor-type impurity level consists of O 2p and Zn 3d. On the other hand, the electrical conductivity and carrier mobility of IZO were evaluated. Comparing the electrical conductivity of IZO with that of its parent material In ₂O₃, it was found that the electrical conductivity increased significantly when Zn-dopant was introduced to In₂O ₃. The higher electrical conductivity of IZQ was considered to be attributed to impurity state and therefore the p-type conductivity.