Development of sensitive detection of crystalline defects in wide gap semiconductor by Raman scattering measurements

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Raman spectra of 3C, 6H, 4H-SiC crystals including stacking faults have been examined using a backscattering geometry. It is found that the intensity of the transverse optical phonon band at 796 cm^<-1>, which corresponds to the phonon mode at the gamma point in 3C-SiC, is sensitive to the stacking faults. We found that the intensity of this band depends on the stacking fault density. These results are explained on the basis of the bond polarizability model. The spatial distribution of the stacking faults is studied by Raman image measurements. The carrier concentration is determined from the line shape analysis of the LO phonon plasmon coupled model. We evaluate the spatial distribution of the carrier concentration and the mobility for modulation-doped 6H-SiC crystals. Our experimental results demonstrate the Raman micro probe imaging is useful to analyze local electrical properties. We also evaluate the polytype phases of the SiC ceramics from Raman probe measurements. The volume contents measured by the Raman intensity of the folded modes of 4H and 15R polytype phases relative to that of the 6H phase in the ceramics are consistent with those determined from x-ray diffraction analysis. We can examine the relation between the spatial distributions of the polytype domains and crystalline grains with a resolution of micro-meter scale.