The variation in nitrogen doping concentration on the (0001¯) facet of 4H-SiC single crystals grown by the physical vapor transport (PVT) growth method was investigated using Raman scattering microscopy. The observed variation was well correlated with the terrace-width variation in the step–terrace structure on the facet; regions with unevenly distributed terrace-widths always showed a lower nitrogen concentration compared to those having evenly distributed terrace-widths. It was revealed by low-energy electron channeling contrast imaging that in lower nitrogen concentration regions, terraces with two dangling bonds per silicon atom at the step riser in the step-down direction always became wider. On the basis of these experimental results, the nitrogen incorporation kinetics during PVT growth of 4H-SiC crystals was discussed.

Enhanced nitrogen doping in the <11−20> directions on the (000−1) facet of 4H-SiC crystals grown by the physical vapor transport (PVT) growth method was investigated using Raman scattering microscopy and atomic force microscopy (AFM). The enhanced nitrogen doping showed either single or double peak structure of nitrogen incorporation in the azimuthal direction around <11−20>. AFM observations revealed that these two characteristic doping structures stemmed from different propagation morphologies of spiral steps on the (000−1) facet. It was also unveiled that the change in the step-flow direction was always associated with the change of the terrace-width ratio on the facet, and that the interplay between these two parameters determined the nitrogen incorporation on the (000−1) facet. On the basis of these experimental results, the mechanism of the azimuthal dependence of nitrogen incorporation on the (000−1) facet during PVT growth of 4H-SiC crystals is discussed.