Raman scattering as a probing method of subsurface damage in SiC

The subsurface damage extension has been investigated in 4H- and 6H-SiC as a function of the size of the polishing abrasive powder. Raman scattering spectra have been collected in the transverse ki//ks⊥c configuration and, from an analysis of the high-frequency longitudinal phonon–plasmon coupled mode, the free carrier density has been evaluated at different distances beneath the sample surface. It was found that the variation of the carrier density depends strongly on the size of the polishing slurry. Moreover, comparing 6H- and 4H-SiC it was found that, for a given slurry 4H-SiC damaged is deeper than 6H-SiC.