A comparative study of photoelectric performance of Ga2O3 solar-blind photodetectors with symmetric and asymmetric electrodes

Abstract

Gallium oxide (Ga2O3) thin films were deposited on quartz substrates under different oxygen flow ratios (O2/[O2+Ar], 0%−5%) by radio-frequency (RF) magnetron sputtering technique followed by thermal annealing at 900 °C for 2 h under N2 atmosphere. The influence of the oxygen concentration on the structural and optical characteristics of Ga2O3 thin films was investigated. The Ga2O3 thin films prepared under an oxygen flow ratio of 1% exhibited optimum crystal quality and the lowest oxygen vacancy (VO) concentration according to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) investigations. All as-prepared polycrystalline Ga2O3 thin film samples exhibited high average transmittance above 87.8% in the visible spectral region and the 0% and 1% thin films had optical bandgap energies of about 4.9 eV. We also fabricated metal−semiconductor−metal (MSM) photodetectors based on 1% Ga2O3 thin films by employing pairs of Ni−Ni symmetrical or Ni−Al asymmetrical interdigitated electrodes. The Ni−Ni photodetector had a high on/off current ratio (Ion/Ioff > 105), a responsivity of 88.7 mA/W, and specific detectivity of 4.81×1010 J at 10 V bias under ultraviolet light-C (UVC) illumination, and the Ni−Al photodetector exhibited self-driven behavior along with short rise and fall times (0.45 s and 0.69 s, respectively).