Residual stress plays a critical role in the structural reliability of large-diameter 4H-SiC crystals grown by physical vapor transport (PVT), yet systematic investigations into its distribution and origin in bulk boules remain limited. In this study, neutron diffraction was used to non-destructively evaluate the internal residual stress distribution in two nitrogen-doped 6-inch 4H-SiC boules with contrasting defect densities. Lattice spacing and residual stress were measured along the direction normal to three principal crystallographic planes — (0004), (11–20), and (–1100)—covering axial and in-plane directions. Both boules exhibited increasing tensile stress along the 〈–1100〉 direction, indicating anisotropic stress behavior. The high-defect boule showed depth-dependent stress inversion along the 〈11–20〉 direction, reflecting defect-induced strain accumulation. These findings highlight the potential of neutron diffraction for internal stress assessment and provide insights for potential thermal field design and process optimization in SiC crystal growth.
Xu et al. (Fri,) studied this question.