Structural characterization of the grown crystal/seed interface of physical vapor transport grown 4H-SiC crystals using Raman microscopy and x-ray topography

Abstract

The defect structure at and near the grown crystal/seed interface of 4H-SiC single crystals grown by the physical vapor transport (PVT) growth method has been investigated using Raman microscopy and x-ray topography. To examine the detailed distribution of crystallographic defects across the interface, 4H-SiC wafers containing a beveled growth interface were prepared from nitrogen-doped 4H-SiC single crystal boules; the beveled interface allows more spatially resolved observations of the defect structure near the interface compared to the interface on vertically sliced [e.g., (112¯0) and (11¯00)] wafers. Raman microscopy imaging using the longitudinal optical phonon-plasmon coupled (LOPC) mode determined the position of the growth interface and revealed several characteristic features of the interface through the analyses of the scattering intensity, peak position, and width of the LOPC mode peak. X-ray topography revealed that there existed networks of basal plane dislocations at the growth interface, and they extended deep inside the seed crystal. Based on these observations, we discussed the defect formation process at the initial stage of PVT growth and suggested an important role of vacancy injection during PVT growth of SiC.