Nucleation mechanism of 6H-SiC polytype inclusions inside 15R-SiC crystals

A model is presented for the nucleation mechanism of 6H-SiC polytype inclusions inside 15R-SiC boules. Inhomogeneous densities of screw dislocations lead to uneven growth rates, resulting in complex step overgrowth processes which can partially suppress the Burgers vector of a 15R 1c screw dislocation through the creation of Frank faults and Frank partial dislocations. Combined with stacking shifts induced by the passage of basal plane partial dislocations, it is shown that the partial Burgers vector suppression can leave behind a residual 6H 1c dislocation, which then acts as a nucleus for reproduction of 6H-SiC structure in the 15R-SiC crystal.