Comparison of GaN and 6H-SiC p-i-n photodetectors with excellent ultraviolet sensitivity and selectivity

We fabricated GaN and 6H-SiC p-i-n photodetectors and compared their electrical and optical characteristics. The GaN diodes suffered from significant leakage current of 37 /spl mu/A/mm/sup 2/ at -5 V, while the SiC diode leakage current was below the noise level at 10 pA/mm/sup 2/ at -20 V. The built-in potentials and the unintentional "i-layer" doping densities were obtained from capacitance-voltage (C-V) measurements. The SiC detectors exhibited a broad spectral response in contrast to the abrupt cutoff observed in the GaN detectors. The peak responsivities of the GaN and SiC photodetectors corresponded to internal quantum efficiencies of 57% at 3.42 eV and 82% at 4.49 eV, respectively. Furthermore, both detectors exhibited excellent visible rejection ratios which is needed for solar-blind applications. The response times at zero bias were 18 and 102 ns for the GaN and SiC detectors, respectively.