Influence of RF Sputtering Temperature on Defects, Transport, and UV-C Photodetection of a-Ga2O3

Abstract

The photodetection capabilities of RF sputtered amorphous thin-film gallium oxide have been studied as a function of their growth temperature. Specifically, X-ray photoelectron spectroscopy (XPS) and dark/UV-C illuminated temperature-dependent current–voltage measurements were used to reveal the relationships among growth temperature, stoichiometry, and photoresponse characteristics. XPS O 1s analysis revealed that an optimum growth temperature of 600 °C yielded the lowest concentration of oxygen vacancies. Devices on this film exhibited the best overall photosensitivity to 254 nm UV-C light, with the highest responsivity (R = 13 A/W) and specific detectivity (D* = 3.7 × 1013 Jones) alongside fast transient response times (τr ∼ 0.51 s, τd ∼ 0.16 s). Lower growth temperatures resulted in films that exhibited increased persistent photoconductivity and proved thermally unstable, failing to recover their original characteristics after heating to 200 °C. Increasing the growth temperature above 600 °C caused increased oxygen deficiency in the films when compared with films grown at 600 °C, likely due to increased out-diffusion of oxygen during deposition. These findings demonstrate that cost-effective, scalable RF sputtering at an optimized growth temperature can produce amorphous gallium oxide with comparable UV-C sensitivity to that achieved with more complex deposition methods.