Observation of surface polarity dependent phonons in SiC by deep ultraviolet Raman spectroscopy

Backscattering Raman spectra of SiC polytype crystals with SiC{0001} polar faces have been measured using deep ultraviolet (DUV), UV, and visible (VIS) excitation sources. We have found that for DUV excitation the intensity profiles of zone-folded modes differ markedly for Si and C faces. This Raman spectral feature is attributed to the presence of nonpropagating phonon modes confined in the near-surface region. It is concluded that the surface-bound phonon modes created with DUV photon field extend over a region a few hundred nanometers in depth, and that the displacements of the phonon modes are anisotropic in the direction of the polar axis. This surface-orientation-dependent Raman spectrum can be used to identify the surface polarity of SiC polytypes.