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 × 10^-3/7.5 × 10^-3/0.83 A/W, UV-to-visible rejection ratio was 2.34 × 10³/1.37 × 10⁴/3.18 × 10⁵, and the detectivity was 2.78 × 10⁸/1.26 × 10⁹/1.17 × 10¹¹ cmHz^0.5W^-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 20and 30-nm Al₂O₃.