Study on Surface Morphology and Polytype Transition of 4H-SiC Single Crystals

The morphology of as-grown surface and polytype transition of 4H-SiC single crystals had been studied by optical microscopy and Raman spectroscopy.The round spiral steps were observed on the facet of 4H-SiC single crystals.There are some slits arrayed along 112-0direction.The surface morphologies at two sides of the slit interface are quite different.From the Raman spectra,it was known that different SiC polytypes are distributed on two sides of the slit.The slits are actually the signs of the polytype-transition process.By observing the longitudinal cut samples,we found that the slits only appear in the interface between 4H-SiC and 15R-SiC rather than other interfaces.As long as the 15R-SiC polytype is produced,it would grow along 0001- and extend radially along the 112-0direction.