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The electrical and optical properties of GaN and 6H-SiC p-i-n photodetectors have been studied. Current-voltage and capacitance-voltage measurements were used in deriving the reverse I-V characteristics, built-in potentials and unintentional doping densities. Results indicate that GaN diodes had significant leakage current, at 37 microA/square millimeter at -5 V, while the SiC leakage current was below the noise level at 10 pA/ square millimeter at -20 V. The SiC detectors showed a broad spectral response while there was an abrupt cutoff in the GaN detectors.

We investigate the optical properties of GaN grown over SiO[sub 2] on SiC substrates by electron cyclotron resonance assisted molecular beam epitaxy. The photoluminescence spectra and refractive index of GaN were compared for GaN/SiO[sub 2]/SiC and GaN/SiC. Strong band-edge luminescence was observed at 3.40 eV from the GaN on both SiO[sub 2]/SiC and on SiC. No defect-related yellow luminescence was observed. The refractive index of GaN at 1.96 eV (632.8 nm) was measured at 2.22 and 2.24 for GaN/SiO[sub 2]/SiC and GaN/SiC, respectively. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]