Investigation of Ga₂O₃-Based Deep Ultraviolet Photodetectors Using Plasma-Enhanced Atomic Layer Deposition System

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 cmHz^1/2W^-1.