【International Papers】SnO₂:F/β-Ga₂O₃ thin-film heterojunctions as sensitive photodetectors for short-wavelength UV radiation

      Researchers from the Sharif University of Technology have published a dissertation titled "SnO₂:F/β-Ga₂O₃ thin-film heterojunctions as sensitive photodetectors for short-wavelength UV radiation" in Results in Physics.

Background

      The photodetectors are commonly based on the semi-conductive materials, and consist of double thin film thin films and conductive electrical contacts. Gallium oxide (β-Ga₂O₃) is a wide-bandgap semiconductor that has garnered significant interest for various applications in electronics and optoelectronics due to its unique properties. Gallium oxide has a band gap of approximately 4.5 to 4.9 eV, depending on its crystalline phase. The most stable phase is the beta (β) phase, which is commonly studied and utilized in applications. Its large band gap also enables it to be transparent to visible light, which is advantageous for UV photodetectors. β-Ga₂O₃ has a high critical electric field (around MV/cm), which allows devices made from this material to handle high voltages without breakdown.

Abstract

      Monitoring UVC radiation from the ozone hole is crucial due to its harmful effects on both the environment and human health. To address this need, photodetectors operating in the short-wavelength ultraviolet (UVC) region are essential. In this study, optical photodetectors based on thin films of fluorine-doped tin oxide (SnO₂:F or FTO) and gallium oxide (β-Ga₂O₃) were fabricated using the spray pyrolysis technique. Initially, individual thin films of SnO₂:F and β-Ga₂O₃ were prepared and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy, and current–voltage (I–V) measurements. Subsequently, photodetectors composed of stacked SnO₂:F/β-Ga₂O₃ thin films were fabricated, and their photoresponse was evaluated by varying the concentration of Ga₂O₃. Among the tested concentrations, the device with 0.2 M Ga₂O₃ exhibited the best performance, with a sensitivity of 6.62 × 10⁻², an external quantum efficiency (EQE) of 233.92 %, and a responsivity of 47.72 mA/W. These results suggest that SnO₂:F/β-Ga₂O₃ thin-film photodetectors are promising candidates for UVC detection and can be effectively utilized in environmental monitoring applications, such as ozone hole observation.

Highlights

      ● FTO/β-Ga₂O₃photodetectors were fabricated via spray pyrolysis and optimized at 0.2  M Ga₂O₃.

      ● Films showed band gaps of 4.59  eV (β-Ga₂O₃) and 3.38  eV (FTO), with superior FTO crystallinity.

      ● The optimized device achieved 47.72  mA/W responsivity and 3.34 × 10⁸ Jones detectivity for UVC monitoring.