Effect of Sn Doping on Structural, Optical, and Electrical Properties of β-Ga ₂ O ₃ Thin Films Prepared via Spin Coating for MSM Photodetector Applications

Due to its ultrawide bandgap and robust physical properties, β-Ga2O3 is a promising candidate for solar-blind UV photodetectors. However, conventional fabrication methods are often costly and complex. In this study, we demonstrate a cost-effective spin-coating technique to fabricate Sn-doped β-Ga2O3 thin films and systematically investigate the effect of Sn concentration on their structural, optical, electrical, and photodetection properties. The results show that controlled Sn doping effectively enhances device performance by tuning the material’s optoelectronic characteristics. Sn-doped β-Ga2O3 thin films were deposited at room temperature onto sapphire substrates using spin coating, with tin concentrations systematically varied from 0 to 20 wt %. X-ray diffraction analysis confirmed that all films crystallized in the monoclinic β-Ga2O3 phase with a nanocrystalline structure. The optical results showed high transmittance in the visible region and a progressive narrowing of the bandgap with increasing concentration of Sn doping. Electrical characterization revealed that the carrier concentration, electrical conductivity, and electron mobility increased with Sn doping up to 15 wt %. However, at 20 wt % Sn, a reduction in mobility was observed, likely due to enhanced carrier scattering or the introduction of defect states. Furthermore, metal–semiconductor–metal (MSM) photodetectors were fabricated to evaluate the influence of increasing Sn wight percentage on device performance. The results demonstrated that with increasing Sn concentration, UV responsivity, detectivity, and response speed were significantly enhanced, highlighting the potential of Sn-doped β-Ga2O3 thin films for high-performance and cost-effective optoelectronic applications.