Carrier Density Dependence of Fano Type Interference in Raman Spectra of p-type 4H-SiC

We have investigated Raman spectra of p-type 4H-SiC crystals with hole concentration ranging from 3×1016 to 1×1021 cm-3. For folded transverse acoustic (FTA) doublet modes, Fano interference profiles were analyzed, and the frequency shift due to Fano interference was obtained as a function of hole concentration. We demonstrated that the shift of the FTA doublet modes is a quantitative measure for evaluating of hole concentration of p-type 4H-SiC. Spectral features of transverse optical (TO) and longitudinal optical phonon-plasmon coupled (LOPC) modes were also studied for various carrier concentrations. The results show that the full width at half maximum of the LOPC and relative intensity of TO and the LOPC can be used as other calibration measures for hole concentration.