In this work, Ga2O3 films were deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system with trimethylgallium precursor and oxygen (O2) plasma. To improve the quality of Ga2O3 films, they were annealed in an O2 ambient furnace system for 15 min at 700, 800, and 900 °C, respectively. The performance improvement was verified from the measurement results of X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The optical bandgap energy of the Ga2O3 films decreased with an increase of annealing temperatures. Metal-semiconductor-metal ultraviolet C photodetectors (MSM UVC-PDs) with various Ga2O3 active layers were fabricated and studied in this work. The cut-off wavelength of the MSM UVC-PDs with the Ga2O3 active layers annealed at 800 °C was 250 nm. Compared with the performance of the MSM UVC-PDs with the as-grown Ga2O3 active layers, the MSM UVC-PDs with the 800 °C-annealed Ga2O3 active layers under a bias voltage of 5 V exhibited better performances including photoresponsivity of 22.19 A/W, UV/visible rejection ratio of 5.98 × 104, and detectivity of 8.74 × 1012 cmHz1/2W-1.
Keywords: X-ray photoelectron spectroscopy spectra; detectivity; gallium oxide films; metal-semiconductor-metal ultraviolet C photodetectors; photoresponsivity; plasma-enhanced atomic layer deposition system.