Characterization of the Free-carrier Concentrations in Doped n-type 4H-and 6H-SiC Crystals by Raman Scattering

LO-phonon-plasmon-coupled modes provide us information on electronic properties in polar semiconductors.We obtained the Raman spectra of n-type 4H-and 6H-SiC crystals and analyzed the effect of doping on Raman spectra.We got the carrier concentrations and damping constants by line-shape fitting of the coupled modes of n-type 4H-and 6H-SiC and Hall measurements,respectively.The results obtained from the two methods agree fairly well.The results indicated that Raman scattering can give the reliable information about the carrier density by analysing the LOPC modes of n-type 4H-and 6H-SiC for low carrier concentrations.