Electronic structure of 6H-SiC(0001)

An electronic structure investigation of Si-terminated 6H-SiC(0001) is reported. The valence-band structure is investigated using photoemission and synchrotron radiation. Recorded valence-band spectra are compared with the partial densities of states obtained in a full-potential linearized augmented plane-wave band-structure calculation. Lower-lying C 2s states give the dominant contribution in spectra recorded at higher photon energies, while higher-lying hybridized C 2p and Si 3s and 3p states dominate at lower photon energies. Assignment of different structures is made from the variation observed in relative intensity with photon energy. The overall agreement between calculated and experimental results is quite satisfactory considering that the experimental studies were conducted on the root 3x root 3-R30 degrees and 6 root 3x6 root 3-R30 degrees reconstructed surfaces, while the calculated results represent the bulk density of states. Significant differences are observed, however. A surface state is identified on the root 3 surface, at 1.3 eV below the Fermi level, and its origin is discussed.