Effect of the deposition temperature and a hydrogen post-annealing treatment on the structural, electrical, and optical properties of Ga-doped ZnO films

Abstract

The combined effects of the deposition temperature and a hydrogen post-annealing treatment on the structural, electrical, and optical properties of Ga-doped ZnO (GZO) films were investigated as a potential substitute for indium tin oxide transparent conductive oxide (TCO). On the as-deposited films, increasing the deposition temperature initially improved the electrical properties, but a deposition temperature in excess of 423 K resulted in the deterioration of the electrical properties due to the development of ZnGa2O4 and Ga2O3 phases originating from the excessive amount of the Ga dopant. While a post-annealing treatment of the GZO films in hydrogen leveled off the overall properties, improvement in the electrical property was observed only in films initially deposited at room temperature. This is attributed to the excessively high concentration of the dopant Ga released from ZnGa2O4 and Ga2O3 during the post-annealing treatment. It is therefore suggested that in the preparation of TCOs based on GZO films, the concentration of the dopant Ga should be carefully controlled to obtain the optimal properties by suppressing the formation of ZnGa2O4 and Ga2O3 that occurs due to the presence of excess Ga.