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 thephysical-vapor-transport (PVT) growth of n-type 4H-SiCsingle-crystal boules are investigated by combining photochemicaletching, transmission electron microscopy, microphotoluminescence,and micro-Raman investigations. SFs with the Si-C bilayer stackingsequence of (3,3) in Zhdanov's notation are found near theseed crystal of the n-type 4H-SiC. Interestingly,we find that the facet region of the n-type 4H-SiCsingle-crystal boule is free of SFs (3,3). Most of the SFs (3,3) areconstrained in the nonfaceted region of n-type 4H-SiC.Micro-Raman analysis indicates that the shear stress exerted in thenonfacet 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 nitrogenconcentrations and growth velocities between the facet and nonfacetregions of the n-type 4H-SiC single-crystal boule,high compressive stress appears in the interface of the facet andnonfacet 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 eliminatesthe generation and expansion of SFs in the 4H-SiC single-crystal boule.