Role of the Growth Facet on the Generation and Expansion of Stacking Faults in PVT-Grown n-Type 4H-SiC Single-Crystal Boules

The generation and expansion of stacking faults (SFs) during the physical-vapor-transport (PVT) growth of n-type 4H-SiC single-crystal boules are investigated by combining photochemical etching, transmission electron microscopy, microphotoluminescence, and micro-Raman investigations. SFs with the Si–C bilayer stacking sequence of (3,3) in Zhdanov's notation are found near the seed crystal of the n-type 4H-SiC. Interestingly, we find that the facet region of the n-type 4H-SiC single-crystal boule is free of SFs (3,3). Most of the SFs (3,3) are constrained in the nonfaceted region of n-type 4H-SiC. Micro-Raman analysis indicates that the shear stress exerted in the nonfacet region gives rise to the formation and expansion of SFs (3,3), which releases the shear stress during the PVT growth of n-type 4H-SiC single-crystal boules. Due to the differences of nitrogen concentrations and growth velocities between the facet and nonfacet regions of the n-type 4H-SiC single-crystal boule, high compressive stress appears in the interface of the facet and nonfacet regions, which impedes the expansion of SFs (3,3). Furthermore, the shear stress in the facet region of a PVT-grown n-type 4H-SiC single-crystal boule is nearly zero, which eliminates the generation and expansion of SFs in the 4H-SiC single-crystal boule.