BAND STRUCTURES OF SI-C AND SI-C-GE ALLOYS

Band structures of Si-C and Si-C-Ge alloys are calculated by using the sb initio LMTO (linear muffin-tin orbital) method within the framewor k of atomic-sphere approximation. The effects of different atomic conf iguration and lattice relaxation on the band structure of alloys are t aken into account. The results show that for large concentrations of C in Si and Si-Ge, the band gap increases monotonically, while for smal l concentrations of C in Si and Si-Ge, the band gap shrinks. The latti ce relaxation further reduces the band gap. The possible explanations for the reduction of band gap of Si-C and Si-C-Ge alloys are presented .