Synchrotron white beam X-ray topography, post-oxidation color mapping, atomic force microscopy and scanning electron microscopy were used to study the defect and polytype distribution in a thin film grown on mesas structures on part of a 4H-SiC crystal subjected to a non-optimal version of a previously reported procedure for achieving atomic flatness. This combination of techniques was used to provide confirmation that atomic flatness could only be achieved on mesas containing no screw dislocations. It was also found that the vast majority of the atomically flat mesas were of small size as expected since the probability of a screw dislocation threading a mesa was proportional to its area. For these small mesas, either no 3C-SiC nucleation or complete coverage by one or other of the 3C variants was observed. In mesas containing screw dislocations, mostly those of larger size, either no 3C nucleation or partial coverage by single or double phase 3C was observed. In contrast to a previous observations of on-axis mesa samples grown under different conditions in which polytypes such as 15R were observed, no polytypes other than 4H, 3C(I) and 3C(II) were detected anywhere on this wafer. In the absence of the stacking sequence template provided by the risers of steps (whether from screw dislocations or off-cut angle), this data indicated that no other polytype forms but 3C under these growth conditions. This study indicated that combined use of synchrotron white beam X-ray topography in back-reflection and forward-reflection geometry, post-oxidation color mapping, atomic force microscopy and scanning electron microscopy, was ideally suited for detailed microstructural and structural mapping in SiC.

Polytype Identification in Heteroepitaxial 3C-SiC Grown on 4H-SiC Mesas using Synchrotron White Beam X-Ray Topography. M.Dudley, W.M.Vetter, P.G.Neudeck: Journal of Crystal Growth, 2002, 240[1-2], 22-33