LOW NOISE P-PI-N GAN ULTRAVIOLET PHOTODETECTORS

We report on the fabrication and characterization of p-pi-n GaN ultrav iolet detectors. The peak responsivity at similar to 363 nm is measure d 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-limite d 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 cur rent to be 2.7 pA at -3 V bias, and a noise density of less than 10(-2 5) A(2)/Hz. the noise floor of the measurement. Extrapolating the nois e data taken at higher reverse biases, we estimate the noise equivalen t power to be 6.6x10(-15) W/Hz(1/2). (C) 1997 American Institute of Ph ysics.