First-principles study on the origin of band-gap reduction in si-lattice matched (formula presented)

M. Ohfuti, Y. Awano, N. Yokoyama

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The electronic structure of a Si-lattice matched (Formula presented) crystal, with (Formula presented) and (Formula presented) is studied using a first-principles energy-band calculation. The state at the bottom of the conduction bands in the (Formula presented) is found to be similar to that in the (Formula presented) crystal with the same x. The band gap of the (Formula presented) crystal is smaller than the unstrained (Formula presented) crystal and agrees with that of the (Formula presented) virtually lattice matched to the (Formula presented) crystal. The band gap of a (Formula presented) crystal with the same y is larger than or equal to that of the Si crystal. It can be concluded that the band-gap reduction in the (Formula presented) crystal is attributed to a lattice shrinkage effect resulting from the introduction of the small C and does not originate from the chemical effect by the introduced C. The calculated coefficient of the band-gap reduction in the (Formula presented) alloy agrees well with that reported for y up to 1% in an experiment, which suggests that the band-gap reduction for the low-C concentrations observed in the experiment may be explained by the origin found numerically for (Formula presented)

Original languageEnglish
Pages (from-to)15515-15518
Number of pages4
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number23
Publication statusPublished - 1999 Jan 1
Externally publishedYes


ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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