On the spiral growth of polytype structures in SiC from a faulted matrix. III. Polytypes based on the 15R and 4H structures

Abstract

The faulted-matrix model of polytypism is applied to the deduction of the most probable series of structures that can result from faulted 15R and 4H matrices in SiC. The different possible intrinsic and extrinsic fault configurations which can occur in the 15R and 4H SiC structures are considered and their relative probability of occurrence determined by calculating the stacking fault energy. It is shown that the most probable fault configuration in 15R depends on whether the 15R structure is stable or metastable in the temperature range in which it is formed. The most probable fault configuration so obtained is considered to lie at different distances from the surface of the basic matrix at the time of the origin of a screw dislocation ledge. Polytype structures that can result from the spiral growth of such faulted ledges of screw dislocations with different Burgers vectors have been deduced. The most probable series of structures are predicted from a calculation of stacking fault energy. The theoretically predicted structures are compared with those experimentally observed.