Stacking faults created by the combined deflection of threading dislocations of Burgers vector c and c+a during the physical vapor transport growth of 4H-SiC

Observations have been made, using synchrotron white beam x-ray topography, of stacking faults in 4H-SiC with fault vectors of kind 1/6 〈 20 2- 3 〉. A mechanism has been postulated for their formation which involves overgrowth by a macrostep of the surface outcrop of a c -axis threading screw dislocation, with two c/2 -height surface spiral steps, which has several threading dislocations of Burgers vector c+a, with c -height spiral steps, which protrude onto the terrace in between the c/2 -risers. Such overgrowth processes deflect the threading dislocations onto the basal plane, enabling them to exit the crystal and thereby providing a mechanism to lower their densities.