EPR and photoluminescence studies of semi-insulating 4H-SiC samples

Several samples of semi-insulating (s.-i.) 4H-SiC have been studied by Electron Paramagnetic Resonance (EPR) at 37 GHz and by photoluminescence (PL). One set of samples revealed EPR spectra of vanadium. The signs of fine structure constants D were determined, at 4.2K, to be positive. In the second set of samples the EPR signals from nitrogen, boron and a deep center, P, with g(parallel to) = 2.0048 and g perpendicular to = 2.0030 appeared in the EPR spectrum after photo excitation of the sample. The P center is postulated to be the deep donor reported previously to be a dominant center in sA. 4H-SiC. Intercenter charge transfer processes between nitrogen and the P center are shown to be very efficient. Both sets of samples revealed the well known vanadium intracenter PL emission lines near 0.95 eV. In addition, a broad band located at 2.43 eV along with sharp near-band-edge luminescence lines has been observed for the samples containing large amounts of vanadium and at 2.38eV with a shoulder at 2.14eV in the samples with low levels of vanadium. (C) 2001 Elsevier Science B.V. All rights reserved.