Mechanism of Polytype Transformation and Related Defect Formation Induced by Carbon Inclusions in 4H‐SiC Crystal

ABSTRACT In the mass production of 8‐inch n‐type 4H‐SiC single crystals, polytype transformations and their associated defects severely degrade crystal quality and electrical performance. In this work, multi‐scale characterization techniques were employed to systematically investigate the formation mechanisms of polytype transformations and their related defects. The results reveal that during the initial growth stage, carbon inclusions deposited at the seed crystal interface disrupt the steady‐state step‐flow growth mode and trigger abnormal reconstructions of the stacking sequence. This further leads to the formation of the secondary 6H‐SiC polytype and induces localized distortions in the stress field, which act as nucleation sites for defects such as micropipes. Optimizing the growth process to effectively regulate the generation and transport of carbon sources is crucial for eliminating carbon inclusions and associated defects, thereby ensuring the stable production of high‐quality 4H‐SiC single crystals.