Interface Shape: A Possible Cause of Polytypes Destabilization during Seeded Sublimation Growth of 15R-SiC
Résumé
We report on the stabilization of 15R Silicon Carbide (15R-SiC) grown by seeded sublimation method. It was found that polytype transitions are directly related to the occurrence of facets on the grown crystals. Once a foreign polytype is formed, its propagation is governed mainly by the interface shape of the crystal and its evolution during growth. A concave crystal shape enhances the expansion of foreign polytypes, usually formed at the periphery of the crystal. Then, foreign polytypes can either overlap the original polytypes (constant concave crystal shape) or form inclusions (change to convex crystal shape). On the contrary, an initially slightly convex interface repels foreign polytypes towards the edge of the crystal. The optimization of the growth interface shape can be a key issue towards the stabilization of bulk 15R-SiC crystals.