Defects analysis in single crystalline 6H-SiC at different PVT growth stages

6H-SiC single crystal was grown by the physical vapor transport (PVT) method. The crystal was cut into several (0001) wafers and two of the wafers were selected for analysis: the wafer close to the surface of the boule (wafer A), and the wafer close to the substrate (wafer B). The wafers were characterized by a double crystal X-ray diffraction rocking curve. The rocking curve of wafer A shows a single symmetrical peak with full widths at half maximum (FWHM) of 40 arcsec, while that of wafer B shows split peaks, which indicate the existence of subgrains. Defects, such as dislocations, micropipes, subgrains etc., in the two wafers were studied by KOH etching combined with optical micrography and X-ray topography. Possible relationships between the observed defects and their formation mechanisms in the growth process are discussed.