Optimization of Heat Transfer Design for High Quality 4H-SiC Ingot Growth

At the high growth temperatures of the PVT method, thermal radiation from the graphite crucible surface to the seed region is the dominant mode of heat transfer. In this study, we propose a newly designed crucible structure with a thinner graphite wall compared to the conventional design for SiC crystal growth. The SiC ingot grown using the conventional crucible exhibited the smallest thickness variation (flat top surface) between the center and the edge of the ingot, accompanied by polytype inclusions, which led to an increase in defect density. In contrast, SiC ingots grown using the newly designed crucibles (Design A and Design B) showed a convex top surface and a significantly lower defect density due to the improved heat transfer efficiency. Thinning the graphite crucible wall helps maintain a relatively higher temperature at the seed edge region, thereby effectively enhancing thermal radiation in the radial direction inside the crucible. These results indicate that thermal radiation in the radial direction can be achieved through appropriate optimization of the graphite wall thickness.