Synchrotron monochromatic beam x-ray topography of 4H-SiC epiwafers was conducted in the conventional grazing incidence reflection 11 \(\overline{2 }\) 8 at 9 keV and also the 2nd order harmonic reflection 22 \(\overline{4 }\) 16 reflection at 18 keV. The contrast of defects on the 22 \(\overline{4 }\) 16 reflection is significantly different from that on the 11 \(\overline{2 }\) 8 due to the deeper penetration of the x-rays. Further, topographs in 22 \(\overline{4 }\) 16 reflection are characterized by weaker background phase contrast from the beryllium window mounted at the exit of the synchrotron x-ray beam. Ray tracing simulations of contrast of threading edge/screw/mix dislocations, and screw type basal plane dislocations on the 22 \(\overline{4 }\) 16 reflections have been performed and good correlations obtained between the simulations and contrast in topographs.
