Photoelectric properties of β-Ga₂O₃ thin films annealed at different conditions

Abstract

In this work, metal–semiconductor–metal solar-blind ultraviolet photoconductors were fabricated based on the β-Ga₂O₃ thin films which were grown on the c-plane sapphire substrates by molecular beam epitaxy. Then, the effects of β-Ga₂O₃ annealing on both its material characteristics and the device photoconductivity were studied. The β-Ga₂O₃ thin films were annealed at 800, 900, 1000, and 1100 °C, respectively. Moreover, the annealing time was fixed at 2 h, and the annealing ambients were oxygen, nitrogen, and vacuum (4.9 × 10⁻⁴ Pa), respectively. The crystalline quality and texture of the β-Ga₂O₃ thin films before and after annealing were investigated by X-ray diffraction (XRD), showing that higher annealing temperature can result in a weaker intensity of $\left( {\bar{4}02} \right)$ diffraction peak and a lower device photoresponsivity. Furthermore, the vacuum-annealed sample exhibits the highest photoresponsivity compared with the oxygen- and nitrogen-annealed samples at the same annealing temperature. In addition, the persistent photoconductivity effect is effectively restrained in the oxygen-annealed sample even with the lowest photoresponsivity.