Application of novel chemical precursors for the preparation of Si-Ge-C heterostructures and superlattices

We have investigated new synthetic methods to Si-Ge-C materials by UHV-CVD and novel chemical precursors. The reactions of (SiH ₃) ₄C and (GeH ₃) ₄C with GeH ₄ and SiH ₄ produce diamond structured materials with the general formula (CS ₄) _xGe _y and (CGe ₄) _xSi _y respectively. These reactions demonstrate the application of novel C-H free precursors that incorporate Si ₄C and Ge ₄C building blocks to prepare single phase materials containing a significant amount of carbon (5-6 at.%). They also indicate the remarkable degree of compositional control provided by the precursor to incorporate the Si ₄C and Ge ₄C molecular framework into the solid state. A range of Si _1-x-yGe _xC _y compositions were also prepared pseudomorphically on [1 0 0] Si at 450-500 °C via reactions of (SiH ₃) ₄C with mixtures of GeH ₄ and SiH ₄. The (Si ₂Ge) ₃₁C ₆ composition appears to display ordering of the Ge and Si atoms in the structure. The incorporation of C in the Si planes seems to provide local strain centers which facilitate the formation of this ordered phase.