BAND STRUCTURE AND DENSITY OF STATES OF β-SILICON NITRIDE

Abstract

The electronic energy band structure of β-Si3N4 has been calculated using the first principles LCAO method. The bottom of the Conduction Band (CB) is at Γ and the top of the valence band (VB) is located along Å line. The very flat top VB along Å accounts for a large hole effective mass. The indirect band gap obtained is very close to the experimental value of 5.2 eV. The density of states (DOS) and partial DOS are also obtained and are in good agreement with photoemission data. In the VB region from -20. to -14. eV the states are entirely composed of N 2s states while in the range from -10.5 eV up, the states are predominately N 2p in character. In the CB region, the DOS is dominated by Si 3s and 3p orbital components. These results are consistant with charge analysis which indicates that on average, 0.56 electron is transferred from Si to N per Si-N bond.