EFFECT OF EXCITATION WAVELENGTH ON THE RAMAN SPECTRUM OF HEXAGONAL DEFECTS IN 4H-SiC

The Raman spectra of 4H- SiC with hexagonal defect have been investigated as a function of the excitation wavelength. As the excitation wavelength increases, the excitation wavelength dependence of Raman spectrum of hexagonal defect is very different from that of the free defect zone in 4H- SiC . Four electronic Raman scattering peaks are seen to be significantly enhanced with longer wavelength excitation. In hexagonal defect, the optical modes ( E 2( TO ), E 1( TO ) and A 1( LO )) and the second-order Raman spectrum are broadened and redshifted as the excitation wavelength increased. But the positions of these bands obtained from the free defect zone do not change within our experimental error. Structure defects are regarded as the origin of those abnormal phenomena in hexagonal defect, and the structure ordering of hexagonal defect may have some similarity with SiC monofilaments.