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 electr ical and optical characteristics. The GaN diodes suffered from significant leakage current of 37 mu A/mm(2) at -5 V, while the SiC diode leakage curre nt was below the noise level at 10 pA/mm(2) at -20 V, The built-in potentia ls and the unintentional "i-layer" doping densities were obtained from capa citance-voltage (C-V) measurements. The SiC detectors exhibited a broad spe ctral response in contrast to the abrupt cutoff observed in the GaN detecto rs. 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, resp ectively. 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.