Effects of intrinsic defects on electronic structure and optical properties of Ga-doped ZnO

This study adopted ab initio methods to calculate the effects of intrinsic defects on the electrical and optical properties of Ga-doped ZnO (GZO). The defective types of GZO considered in this study include O vacancies (GaZnVO), Zn vacancies (GaZnVZn), interstitial O (GaZnOi), and a non-defective type (Ga-Zn). The results for calculating formation energy show that, during the GZO preparation process, the growth environment influences the type of intrinsic defects that occur. Under poor O conditions, a GaZnVO structure is most likely to form; conversely, under rich O conditions, GaZnVZn or GaZnOi is most likely to form. The calculated results regarding band structure and density of states indicate that the V-O defect present in the GaZnVO model produces a deep donor level, which substantially reduces transmittance. The V-Zn and O-i defects in GaZnVZn or GaZnOi models reduce carrier concentration and mobility. Subsequently, reduced carrier concentration and mobility significantly increase resistivity. The Ga-Zn structure can be fabricated by introducing appropriate O flow rates during the preparation process. This structure possesses superior photoelectric features. The results obtained in this study were compared with previous experimental literature to explain the potential reasons for the shift in electrical and optical properties under varying O flow rates. (C) 2014 Elsevier B.V. All rights reserved.