  Two 75mm 4H-SiC single crystals are grown by the physical vapor transport
(PVT) technique, using different insulation materials. The insulation material
of higher thermal conductivity led to an increased radial temperature gradient.
The evolution of the growth front was monitored using the in-situ computed
tomography (CT). A slightly bent growth interface and a bigger facet are formed
during the growth applying a lower radial temperature gradient while a smaller
facet and steeper crystal flanks are formed in the case of the larger radial
temperature gradient. Micropipes are deflected laterally by large surface steps
on the steep crystal flanks and a reduction of threading edge dislocations by
60% is revealed by KOH defect etching.
