Effects of post-deposition annealing temperature in nitrogen/oxygen/nitrogen ambient on polycrystalline gallium oxide films

Polycrystalline Ga2O3 films were obtained after post-deposition annealing of as-deposited Ga2O3 films via radio frequency magnetron sputtering at different temperatures (400, 600, 800, and 1000 degrees C) in nitrogen/oxygen/ nitrogen ambient. The Ga2O3 films obtained at lower temperatures (400 and 600 degrees C) demonstrated semiconducting property while the films obtained at higher temperatures (800 and 1000 degrees C) demonstrated insulating property based upon the leakage current density-voltage characteristics. The semiconducting properties were originated from the presence of oxygen vacancies as well as nitrogen incorporation as the scattering centre in the films, which could serve as the conducting path of electrons, encouraging a higher leakage current. The acquisition of a smaller direct and indirect band gap by these films further supported the fact that electrons would overcome the potential barrier easier. On the other hands, the presence of oxygen vacancies and nitrogen incorporation as well as preferred orientation of film growth accompanied with dislocation affected the leakage current density-voltage characteristics. Detailed investigation in the aspects of structural, morphological, optical, and electrical characteristics of the films was demonstrated.