Ga-Doped ZnO/GaN Schottky Barrier UV Band-Pass Photodetector with a Low-Temperature-Grown GaN Cap Layer

Abstract

Ga-doped ZnO (GZO) films were deposited onto low-temperature-grown (LTG) GaN/i-GaN (PD-I) and i-GaN (PD-II) epitaxy layers to form Schottky barrier UV band-pass photodetectors (PDs). The UV PDs exhibited a narrow band-pass spectral response ranging from 330 to 380 nm. It was also found that by using an LTG GaN layer on top of conventional nitride-based UV PDs, the leakage current was significantly reduced and a much larger photocurrent-to-dark-current contrast ratio was achieved. The short-wavelength cutoff at around 330 nm can be attributed to the marked absorption of the GZO top contact layer. The zero-bias peak responsivities were estimated to be 0.13 and 0.08 A/W at 360 nm for PD-I and PD-II, respectively. When the reverse bias was below -10 V, the dark current of PD-I was considerably below 20 pA.