Effects of the thermal field on the diameter enlargement of 200 mm SiC by PVT method

Expanding the diameter and reducing the defect density of 4H silicon carbide (4H-SiC) single crystals are key development trends and primary challenges in the preparation of 4H-SiC single-crystal substrates. During the physical vapor transport (PVT) process, the thermal field is regulated by the furnace configuration and temperatures of the monitoring points, while crystal diameter enlargement is facilitated by the bevel of the crucible. In this study, experiments on enlarging the diameter of 200 mm 4H-SiC crystals have been conducted, with the radial and axial temperature gradient controlled by adjusting the shape of the graphite insulation and the temperatures of the monitoring points. The increase in radial temperature gradient successfully eliminated marginal polycrystals and polytype inclusions. Besides, increasing the radial or axial temperature gradient led to larger expanding angles, greater thickness, and increased diameters of the SiC ingots. We also proposed a growth mechanism to explain the elimination and generation of foreign polytypes. Furthermore, the densities of micropipes (MPs) and the electrical resistivities indicated good qualities of the wafers at the latest growth stage. Our work offers valuable insights into growing high-quality large-diameter SiC single crystals using the PVT method.