A method for estimating the defects density in SiC bulk crystals by defect-selective etching in molten KOH has already been successfully demonstrated. In this paper, the results of applying this technique to bulk SiC crystals are reported. Etching produced hexagonal pits on the Si-polar （0001） plane,while round pits formed on the C face. The etching rate and the nature of etch pits for SiC depends on the growth process. For SiC crystals grown by the PVT process with high growth gas flow rate,the edge and screw dislocation density and the MP density are about 2. 82 × 10^5 ,94,and 38cm^-2 ,respectively. For SiC crystals grown by the PVT process with low growth gas flow rate,those defects densities are about 9.34 × 10^5 ,2, and 29cm^-2 respectively. The results indicate that as the growth gas flow rate increases, the edge dislocation density decreases to avoid N2 impurity.
