O2-to-Ar Ratio-Controlled Growth of Ga2O3 Thin Films by Plasma-Enhanced Thermal Oxidation for Solar-Blind Photodetectors

Ga2O3 is an ultra-wide bandgap semiconductor material that has attracted significant attention for deep ultraviolet photodetector applications due to its excellent UV absorption capability and reliable stability. In this study, a novel plasma-enhanced thermal oxidation (PETO) method has been proposed to fabricate Ga2O3 thin films on the GaN/sapphire substrate in the gas mixture of Ar and O2. By adjusting the O2-to-Ar ratio (2:1, 4:1, and 8:1), the structural, morphological, and photoelectric properties of the synthesized Ga2O3 films are systematically studied as a function of the oxidizing atmosphere. It is demonstrated that, at an optimal O2-to-Ar ratio of 4:1, the synthesized Ga2O3 thin film has the largest grain size of 31.4 nm, the fastest growth rate of 427.5 nm/h, as well as the lowest oxygen vacancy concentration of 16.61%. Furthermore, the nucleation and growth of Ga2O3 thin films on the GaN/sapphire substrate by PETO is proposed. Finally, at the optimized O2-to-Ar ratio of 4:1, the metal–semiconductor–metal-structured Ga2O3-based photodetector achieves a specific detectivity of 2.74×1013 Jones and a solar-blind/visible rejection ratio as high as 116 under a 10 V bias. This work provides a promising approach for the cost-effective fabrication of Ga2O3 thin films for UV photodetector applications.