Reduced graphene oxide on α-Ga2O3 with adjustable Schottky barrier for solar-blind UV detection

α-Ga2O3 is a promising material platform for solar-blind ultraviolet photodetectors. Among the various device architectures, metal–semiconductor–metal (MSM) structures are attractive because they offer simple fabrication and high sensitivity; however, their performance strongly depends on the quality of the Schottky contact. Reduced graphene oxide (rGO) is a suitable electrode material owing to its high UV-C transparency, tunable work function, and good Schottky contact with Ga2O3. This work fabricated rGO/α-Ga2O3 MSM solar-blind photodetectors (SBPDs) and systematically controlled the rGO properties, such as sheet resistance, optical transmittance, and Schottky barrier height (SBH) through thermal reduction. Increasing the reduction temperature yielded increasingly deoxygenated rGO, resulting in a work function shift that decreased the SBH. The optimized device using rGO reduced at 350 °C showed a high wavelength selectivity of 3.40 × 104 without an external filter and a detectivity of 4.85 × 1015 Jones at 254 nm. These results demonstrate that controlling the reduction temperature of rGO is a scalable and straightforward method for balancing the transparency, conductivity, and SBH to achieve high-performance Ga2O3-based MSM SBPDs.