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Raman characterization of local electrical properties and growth process in modulation-doped 6H-SiC crystals J. Appl. Phys. 95, 3547 (2004); 10.1063/1.1655682Raman scattering from LO phonon-plasmon coupled modes and Hall-effect in n-type silicon carbide 4H-SiC Raman spectroscopy has been used to investigate wafers of both 4H-SiC and 6H-SiC. The wafers studied were semi-insulating and n-type ͑nitrogen͒ doped with concentrations between 2.1ϫ10 18 and 1.2ϫ10 19 cm Ϫ3 . Significant coupling of the A 1 longitudinal optical ͑LO͒ phonon to the plasmon mode was observed. The position of this peak shows a direct correlation with the carrier concentration. Examination of the Raman spectra from different positions on the wafer yielded a rudimentary spatial map of the carrier concentration. These data are compared with a resistivity map of the wafer. These results suggest that Raman spectroscopy of the LO phonon-plasmon mode can be used as a noninvasive, in situ diagnostic for SiC wafer production and substrate evaluation.

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