Effect of crystal anisotropy on the infrared reflectivity of 6H-SiC

Polarized infrared reflectivity spectra of 6H-SiC single crystals under different angles of incidence are reported. A new sharp line in the reststrahl band was observed in the extraordinary ray, whose line shape is dependent on the angle of incidence. It was possible to show that crystal anisotropy of 6H-SiC is the reason for the new line in the reflectivity spectrum. A numerical calculation using a Lorentz oscillator model confirmed this result. Two weak one-phonon absorption lines in the reststrahl-band region for E∥c were observed. Furthermore, we found a line at 859 ${\mathrm{cm}}^{\mathrm{-}1}$ in the extraordinary ray and an unusual structure near ${\mathrm{\omega }}_{\mathrm{TO}}$ in the reststrahl band of parallel c-cut 6H-SiC samples, which could not be explained in terms of the classical Lorentz oscillator model.