Dependence of energy gaps and effective masses on atomic positions in hexagonal SiC

We have performed several band structure calculations on 2H-, 4H-, and 6H-S iC, using different lattice constants and basis atom positions in order to investigate the sensitivity of the electronic structure and explain the dis crepancies in band structure results between different authors. It is shown that even small changes in the basis atom positions have a strong impact o n the crystal-field splitting, whereas the relative changes in the fundamen tal band gap, the spin-orbit splitting, and the effective electron and hole masses are practically negligible. The computational method was based on t he local density approximation within the density functional theory. (C) 19 99 American Institute of Physics. [S0021-8979(99)01721-1].