AlGaN/GaN Schottky-barrier photodetectors with 7.5, 15, 30 and 60-nm-thick low temperature GaN cap layers were fabricated. It was found that dark currents were small for these detectors. With an incident light wavelength of 320 nm, it was found that measured peak responsivities were 0.07, 0.05 and 0.03 A/W while UV to visible rejection ratios were 700, 160 and 20 for the photodetectors with 15, 30 and 60-nm-thick low temperature GaN cap layers, respectively. (c) 2005 Elsevier B.V. All rights reserved.