Defect levels and types of point defects in high-purity and vanadium-doped semi-insulating 4H-SiC

Electron paramagnetic resonance (EPR) spectroscopy and photo-induced EPR are used to examine the point defects in vanadium-doped 4H-SiC and high-purity semi-insulating (HPSI) 4H-SiC grown by physical vapor transport. Both types of samples often exhibit a 1.1-eV activation energy, E-a, as extracted from the temperature-dependent Hall/resistivity measurements; however, different defects are related to the same E-a in each case. In the vanadium-doped wafers, the EPR data reveal both V4+ and V3+ in the same sample; thus, the 1.1-eV Hall activation energy is tentatively interpreted as the V3+/4+ acceptor level. However, this conclusion cannot be confirmed because additional defects complicate the photoresponse of vanadium. The carbon vacancy, which is detected in all the HPSI wafers, exhibits a range of photothresholds similar to the various values measured for E-a. The photo-EPR and temperature-dependent Hall/resistivity measurements made before and after a 1600degreesC anneal suggest that several different types of nonuniformly distributed defects participate in compensation of the HPSI material and that annealing selectively removes those with different defect levels. (C) 2004 American Institute of Physics.