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 305nm and an applied bias of 5V, it was found that peak responsivities were 0.02, 0.005 and 0.007A/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 1.55×1010cmHz0.5W−1, respectively.