Si-C atomic bond and electronic band structure of a cubic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>alloy

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We apply the ${\mathrm{sp}}^{3}{s}^{*}$ tight-binding model to study the electronic energy band structure of the cubic ${\mathrm{Si}}_{1\ensuremath{-}y}{\mathrm{C}}_{y}$ alloy. First by the effective medium approximation where local atomic fine structures are averaged out, it is obtained that the energy band gaps of both relaxed and strained ${\mathrm{Si}}_{1\ensuremath{-}y}{\mathrm{C}}_{y}$ alloys increase with increasing C content. The effect of the local Si-C atomic bond structure on the energy band is studied in the real space in order to include the actual broken translational symmetry in the ${\mathrm{Si}}_{1\ensuremath{-}y}{\mathrm{C}}_{y}$ alloy. The electronic local densities of states are investigated and the following is concluded: (a) When Si-C bond length in the alloy assumes the crystal SiC one (strained alloy), an electronic state at the C atom and its surrounding Si atoms is induced in the energy band gap of crystal Si. The valence band edge is slightly lifted. The results indicate a type I energy band alignment for strained ${\mathrm{Si}}_{1\ensuremath{-}y}{\mathrm{C}}_{y}/\mathrm{Si}$ quantum well. (b) When the Si-C bonds assume the Si-Si bond length of the crystal Si (relaxed alloy), the electronic states are not much modified.

Journal

  • Physical Review B

    Physical Review B 58 7717-7722, 1998-09-15

    American Physical Society (APS)

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