AlGaN MSM photodetectors with recess-etched LT-AlGaN cap layers

AlGaN metal-semiconductor-metal photodetectors with recess-etched low temperature (LT)-AlGaN cap layers were fabricated. It was found that photocurrent can be enhanced and a sharp cut-off can be achieved by etching away the LT-AIGaN cap layer in the light absorption region while keeping the LT-AIGaN cap layer under the contact electrodes. It was also found that dark leakage current can be reduced by passivating the damaged surface with SiO₂ film. Furthermore, it was found that, a photocurrent to dark current contrast ratio of 688 and ultraviolet to visible contrast ratio of 141 was achieved from the recess-etched photodetector with passivation.