Substrate-bias-aided preparation and properties of amorphous gallium oxide films and their deep-ultraviolet photodetectors

Amorphous gallium oxide (a-GaOx) thin films are fabricated via magnetron sputtering at room temperature by regulating the substrate bias voltage (Vs) in a wide range (0 ~ -184 V). The effect of Vs on the performance of a-GaOx films and their photodetector devices, such as the chemical composition, optical, morphological, and electrical properties, are systematically investigated. It's found that both the refractive index and the film relative mass density are highly dependent on the Ga/O ratio that can be effectively modified by the Vs. And the subband trap density or/and microvoid defects in a-GaOx films can be largely reduced under a well-selected Vs. The deep-ultraviolet photodetectors based on the optimized a-GaOx thin films show a responsivity of nearly 13 A/W with an ultrahigh UV/vis. rejection ratio. The research suggests that substrate bias voltage may be a feasibly subsidiary method for low-temperature magnetron sputtering technology with respect to the quality control of a-GaOx films.