【International Papers】Ag/Ga₂O₃/n-Si Schottky-type photodetector for visible light detection

      Researchers from the Suleyman Demirel University have published a dissertation titled "Ag/Ga₂O₃/n-Si Schottky-type photodetector for visible light detection" in Journal of Materials Science: Materials in Electronics.

Background

      Ga₂O₃-based photodetectors can be enhanced to detect light over a wide spectrum with their excellent high sensitivity performance . The aim of this study is to combine infrared absorption of Si and UV absorption of Ga₂O₃ to obtain visible light photodetectors. In this work, Ga₂O₃ nanostructures were deposited on an n-Si substrate by electrodeposition technique, and their structural and morphological properties were examined by XRD, SEM and EDX analysis. As a result, grain sizes, surface morphologies, and chemical compositions of Ga₂O₃ nanostructure samples were determined. Afterward, the photodetector structures of Ga₂O₃ samples were designed and fabricated. The characterizations of the fabricated heterojunctions were obtained by I-V measurements for various light power illumination intensities and various wavelengths. Thus, photodetector parameters such as responsivity, detectivity, and EQE of the Ag/Ga₂O₃/n-Si Schottky photodetector were extracted.

Abstract

      Gallium oxide (Ga₂O₃) is an ultra-wide band gap material which has been receiving increasing interest for its potential applications in power electronics, ultraviolet (UV) photodetectors, and gas sensors. In this study, we have synthesized β-phase Ga₂O₃ on n-Si substrate using the electrodeposition technique, and investigated its properties for use in photodetector applications for broadband detection combining Si and Ga₂O₃. X-ray diffractometer (XRD), scanning electron microscope (SEM) with energy dispersive x-ray (EDX) analysis were conducted to illuminate structural and morphological behaviors of the Ga₂O₃. Ag metallic contacts on the Ga₂O₃/n-Si junction and Al ohmic contact on the back surface of the n-Si were obtained by thermal evaporation technique. Thus, Ag/Ga₂O₃/n-Si Schottky-type photodetectors were fabricated and characterized by current–voltage (I-V) measurements depending on various light power intensities and wavelengths ranging from UV to near-infrared (NIR). The diode characteristics, as well as the photodetection parameters such as responsivity, specific detectivity, and external quantum efficiency (EQE) were determined and discussed in detail. The Ag/Ga₂O₃/n-Si Schottky-type photodetectors showed high performances: 122.88 A/W responsivity, 1.07 × 10¹² Jones specific detectivity, and very high EQE value of 2.18 × 10⁴% at 700 nm wavelength. The obtained Ag/Ga₂O₃/n-Si Schottky-type photodetector exhibits promising potential as a candidate for optoelectronic applications in the visible range. These photodetectors can be used in visible light communication, light sensing and cameras.

Conclusion

      We synthesized Ga₂O₃ nanostructures on n-Si substrates by electrodeposition technique and characterized the structures by XRD, SEM, and EDX analysis. The XRD pattern confirmed the monoclinic crystalline structure of the β-phase Ga₂O₃ nanostructures, and the crystalline size was determined at about 15–40 nm by various methods. While the SEM image revealed rod-like structures on the surface of n-Si, EDX analysis confirmed stoichiometry Ga₂O₃. The Ga₂O₃/n-Si heterostructures were coated with Ag contacts to fabricate Ag/Ga₂O₃/n-Si Schottky-type photodetector. Ag/Ga₂O₃/n-Si was characterized by I-V measurements for various light power densities for AM 1.5 sunlight and wavelengths from 351 to 800 nm at 30 mW/cm². The device parameters of the Ag/Ga₂O₃/n-Si junction were extracted from I-V characteristics using thermionic emission theory, Norde, and Cheung methods. The ideality factor and barrier height values were obtained as 2.53 and 0.62 eV, respectively. The photocurrent, photosensitivity, responsivity, and specific detectivity values were determined for light power density and wavelength changes. The Ag/Ga₂O₃/n-Si Schottky-type photodetector has exhibited 122.88 A/W responsivity, 1.07 × 10¹² Jones specific detectivity at 700 nm wavelength value. The photodetector exhibited a very high EQE value of 2.18 × 10⁴% at 700 nm, demonstrating good optoelectronic characteristics from UV to NIR region.