SiC is considered to be a good candidate for high-power device materia
l. For this application, however, large (> 1 cm2), defect-free areas m
ust be available in SiC wafers. In the present work, commercially avai
lable Lely and modified Lely grown single crystal 6H-SiC wafers have b
een analyzed as to their large-area structural quality. Scanning elect
ron microscopy (SEM) and high resolution X-ray diffractometry (HRXRD)
have been utilized. The latter technique was used to conduct reciproca
l space mapping about on- and off-axis reciprocal lattice points (RLPs
). SEM analysis showed the existence of macro-defects such as pin-hole
s, pits and inclusions in the modified Lely material, while HRXRD-RLP
analyses showed the effects of a mosaic structure. These data indicate
d the presence of a domain structure, with varying domain densities. T
hese results are discussed in the context of the SiC growth process. T
he possibility of a relationship between these macro-defects and the g
rowth spiral mechanism is presented.