AlGaN ultraviolet metal-semiconductor-metal photodetectors grown on Si substrates

AlGaN ultraviolet metal-semiconductor-metal photodetectors (PDs) with low temperature (LT)-AlN and LT-GaN cap layers were prepared on Si substrates. Unlike PDs prepared on sapphire substrates, no markedly reduction in dark current was observed from the PD with LT-GaN cap layer. With an incident wavelength of 305 nm and an applied bias of 5 V, it was found that peak responsivities were 0.02, 0.005 and 0.007 A/W for the PDs with LT-AlN cap layer, with LT-GaN cap layer and without cap layer, respectively. The corresponding detectivities were 2.2 × 1010, 1.36 × 1010 and 1.55 × 1010 cm Hz0.5 W−1, respectively.