Different roles of a boron substitute for carbon and silicon in β-SiC

The first-principles numerical simulation is employed to calculate the effect of replacement of carbon and silicon with boron on the electronic structure and optical properties of β-SiC. Mulliken analysis shows that the B impurity bond lengths shrink in the case of B_Si, while they expand with reference to B_C. In addition, B_Si contains C - C, Si - Si and B - Si bonds. The calculated results show that the two systems of B_C and B_Si apply different dispersion. B_C is in accordance with the Lorentz dispersion theory while B_Si follows the Drude dispersion theory. Theoretic analysis and quantitative calculation are used for conductivity spectra in the infrared region.