Low noise p-pi-n GaN ultraviolet photodetectors

We report on the fabrication and characterization of p-pi-n GaN ultraviolet detectors. The peak responsivity at similar to 363 nm is measured to be 0.1 A/W in the photovoltaic mode, and 0.14 A/W with a bias of -15 V, Speed measurements have shown the photoresponse to be RC-limited with the response time decreasing from 17.4 ns at zero bias to 10.3 ns at -6 V bias. For a 200x200 mu m(2) device, we measure the dark current to be 2.7 pA at -3 V bias, and a noise density of less than 10(-25) A(2)/Hz. the noise floor of the measurement. Extrapolating the noise data taken at higher reverse biases, we estimate the noise equivalent power to be 6.6x10(-15) W/Hz(1/2). (C) 1997 American Institute of Physics.