Growing Al2O3 by Ultrasonic Spray Pyrolysis for Al2O3/AlGaN/GaN Metal-Insulator-Semiconductor Ultraviolet Photodetectors

This paper proposed Al
₂
O
₃
deposition by ultrasonic spray pyrolysis (USP) method as an insulator layer for Al
₂
O
₃
/AlGaN/GaN metal-insulator-semiconductor ultraviolet photodetector (MIS-UV-PD) applications. The composition of USP-grown Al
₂
O
₃
was confirmed by X-ray photoelectron spectroscopy. The refractive index and transmittance characteristics of USP-grown Al
₂
O
₃
were also characterized. The Al
₂
O
₃
/AlGaN/GaN MIS-UV-PD performances with different Al
₂
O
₃
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 × 10
³
/1.37 × 10
⁴
/3.18 × 10
⁵
, and the detectivity was 2.78 × 10
⁸
/1.26 × 10
⁹
/1.17 × 10
¹¹
cmHz
^0.5
W
^-1
for the MIS-UV-PD with 30-/20-/15-nm-thick Al
₂
O
₃
. It was found that the performances of MIS-UV-PD with 15-nm Al
₂
O
₃
as the insulator layer are much better than the MIS-UV-PD with 20and 30-nm Al
₂
O
₃
.