Growth defect studies in SiC single crystals

Growth defects in vapor grown 6H-SiC single crystals have been studied using a combination of techniques, including: synchrotron white beam x-ray topography (SWBXT), conventional optical microscopy, fluorescence microscopy, and epi-fluorescence laser scanning confocal microscopy (LSCM). These studies of crystal sections cut both parallel and perpendicular to the [0001] growth axis focused on growth dislocations of screw character running approximately parallel to the growth axis. SWBXT back-reflection and transmission images are presented of these dislocations, which are known to possess a range of Burgers vector magnitudes, and in the case of large Burgers vector magnitude, hollow cores, known as micropipes. Results of detailed LSCM and fluorescence microscopy imaging of these micropipes are presented and discussed in the light of the SWBXT images. Detailed SWBXT studies further reveal that slip dislocations lying in the (0001) plane are connected to the growth dislocations, and appear to emanate from them, periodically along their lengths, in the form of loops. The periodicity, along the superscrew dislocations, of these dislocation generation phenomena, is found to be very similar to the periodicity of dilation and constriction phenomena in the associated micropipes, as measured by LSCM and fluorescence microscopy. This suggests that the two phenomena may be related.