Polytype formation in silicon carbide single crystals

SiC single crystals were grown on the seeds with different root-mean-square (RMS) roughness by physical vapor transport (PVT) method. Green and yellow zones appeared in the same wafer. Decreasing the RMS roughness, the yellow zone was increased and the wafer was uniform. The green and yellow zones corresponded to 6H and 4H polytype, respectively. Based on Raman spectra and structural characterization, SiC polytype formation mechanism was discussed. It was found that the polytype was dependent on the seed RMS roughness.