Growing Al₂O₃ by ultrasonic spray pyrolysis for Al₂O₃/AlGaN/GaN metal-insulator-semiconductor ultraviolet photodetectors

This paper proposed Al₂O₃ deposition by ultrasonic spray pyrolysis (USP) method as an insulator layer for Al₂O₃/AlGaN/GaN metal-insulator-semiconductor ultraviolet photodetector (MIS-UV-PD) applications. The composition of USP-grown Al₂O₃ was confirmed by X-ray photoelectron spectroscopy. The refractive index and transmittance characteristics of USP-grown Al₂O₃ were also characterized. The Al₂O₃/AlGaN/GaN MIS-UV-PD performances with different Al₂O₃ thickness (30, 20, and 15 nm) were investigated. The responsivity was 1.3 \times 10^{-3}/7.5 \times 10^{-3}/0.83 A/W, UV-to-visible rejection ratio was 2.34 \times 10^{3}/1.37 \times 10^{4}/3.18 \times 10^{5} , and the detectivity was 2.78 \times 10^{8}/1.26 \times 10^{9}/1.17 \times 10^{11} cmHz ^{0.5} W ^{-1} for the MIS-UV-PD with 30-/20-/15-nm-thick Al₂O₃. It was found that the performances of MIS-UV-PD with 15-nm Al₂O₃ as the insulator layer are much better than the MIS-UV-PD with 20-and 30-nm Al₂O₃.