Using Ray Tracing Simulations for Direct Determination of Burgers Vectors of Threading Mixed Dislocations in 4H-SiC c-Plane Wafers Grown by PVT Method

The presence of threading mixed dislocations (TMDs) (with both edge and screw component) in 4H-SiC crystals grown by PVT method has been reported both from axial slices (wafers cut parallel to the growth axis) and commercial offcut wafers (cut almost perpendicular to the growth axis). In this paper, a systematic method is developed and demonstrated to unambiguously determine the Burgers vectors of TMDs in 4H-SiC commercial offcut wafers using both Synchrotron Monochromatic X-ray Topography (SMBXT) and Ray Tracing Simulations. The principle of this method is that the contrast of dislocations on different reflections varies with the relative orientation of Burgers vectors with respect to the diffraction vectors. Measurements confirm that in commercial offcut wafers the majority of the threading dislocations with screw component are mixed type dislocations.