Deep ultraviolet raman microspectroscopic characterization of polishing-induced surface damage in SiC crystals

We have investigated polishing-induced surface damage in nitrogen-doped {0001} 4H-SiC crystals with silicon and carbon faces through deep ultraviolet Raman microspectroscopy. The structural and electrical properties of the damaged layers were characterized as a function of the abrasive particle size, using pure phonon modes and a longitudinal-optical-phonon plasmon coupled mode as monitor bands. The degree of damage decreased with the size. Although abrasive polishing with finer particles enables the long-range order of the lattice to almost fully recover, the carrier density remains partly reduced in the polished surface layers. The number of defects that induces a reduction in the free carrier density differs between the Si and C faces of 4H-SiC crystals.