Reduction of dark current in AlGaN-GaN Schottky-barrier photodetectors with a low-temperature-grown GaN cap layer

AlGaN-GaN-based UV Schottky-barrier photodetectors with (i.e., sample A) and without (i.e., sample B) the low-temperature (LT) GaN cap layer were both fabricated. It was found that we could achieve a lower leakage current from sample A. Under reverse bias, it was found that sample A showed a dark current as low as 2×10^-11 A at -5 V. In contrast, the dark current of sample B was at least one order of magnitude larger. With an incident light wavelength of 320 nm and a -1 V reverse bias, the measured responsivity was around 0.03 and 0.015 A/W for samples A and B, respectively.