Polytype switching identification in 4H-SiC single crystal grown by PVT

Generally, it is very difficult to grow large diameter 4H-SiC single crystal with single polytype by Physical Vapor Transport (PVT) growth method and mostly it ends up with the presence of some other polytypes (viz. 6H, 15R). This paper presents the various comprehensive polytype identification techniques in SiC wafer grown by PVT method. Characterization techniques, viz. X-Ray diffraction, Scanning electron microscopy, Cathodoluminescence (CL) and Raman spectroscopy, are used in the present study in order to identify the presence of 4H, 6H and 15R polytype region in SiC wafer. Raman mapping (using phonon frequencies at 150, 171, 203 cm(-1) for 6H, 15R and 4H, respectively) and X-Ray Topography [using grazing incidence asymmetric plane (11-2 8) for 4H-SiC, (11-2 12) for 6H-SiC and (11-2 30) for 15H-SiC] and CL spectra (defect state peak positions at similar to 500 nm and 580 nm for 4H and 6H, respectively) are proposed to distinguish the switching of polytypes in a large area SiC wafer. The polytype switching in SiC ingot may occur because of temperature fluctuations during the sublimation growth process.