ULTRAVIOLET-SENSITIVE, VISIBLE-BLIND GAN PHOTODIODES FABRICATED BY MOLECULAR-BEAM EPITAXY

GaN p-i-n photovoltaic diode arrays were fabricated from epitaxial fil ms deposited on sapphire by molecular beam epitaxy. Peak UV responsivi ty was 0.11 A/W at 360 nm, corresponding to 48% internal quantum effic iency. Visible rejection over 400-800 nm was 3-4 orders of magnitude. Typical pulsed time response was measured at 8.2 mu s. Spectral respon se modeling was performed to analyze the photocurrent contributions fr om photogenerated carrier drift in the depletion region and from minor ity carrier diffusion in the p and n layers. With the model, a maximum internal quantum efficiency of 55% at 360 nm was calculated for the p hotovoltaic diode structure. (C) 1997 American Institute of Physics.