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.

A novel characterization method for the nitrogen doping concentration in heavily nitrogen-doped (more than 1 × 10 19 cm −3 ) 4H-SiC crystals using Raman scattering microscopy is proposed. The method utilizes the integrated intensity of the longitudinal optical phonon-plasmon coupled (LOPC) mode signal arising at 1100 cm −1 , which exhibits marked changes in the peak position, intensity, and line shape when the nitrogen concentration in 4H-SiC crystals changes. The proposed method showed a much higher sensitivity to the nitrogen doping variation in 4H-SiC crystals compared to the conventional characterization methods using the LOPC peak shift and the Fano interference, and detected a small variation (∼1%) in the nitrogen doping concentration across the (000 1) facet of heavily nitrogen-doped 4H-SiC crystals.