Stabilizing the surface morphology of Si1-x-yGexCy/Si heterostructures grown by molecular beam epitaxy through the use of a silicon-carbide source

E. T. Croke, J. J. Vajo, A. T. Hunter, C. C. Ahn, D. Chandrasekhar, T. Laursen, David Smith, J. W. Mayer

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Abstract

Si1-x-yGexCy/Si superlattices were grown by solid-source molecular beam epitaxy using silicon carbide as a source of C. Samples consisting of alternating layers of nominally 25 nm Si1-x-yGexCy and 35 nm Si for 10 periods were characterized by high-resolution x-ray diffraction, transmission electron microscopy (TEM), and Rutherford backscattering spectrometry to determine strain, thickness, and composition. C resonance backscattering and secondary ion mass spectrometries were used to measure the total C concentration in the Si1-x-yGexCy layers, allowing for an accurate determination of the substitutional C fraction to be made as a function of growth rate for fixed Ge and substitutional C compositions. For C concentrations close to 1%, high-quality layers were obtained without the use of Sb-surfactant mediation. These samples were found to be structurally perfect to a level consistent with cross-sectional TEM (<107 defects/cm2) and showed considerably improved homogeneity as compared with similar structures grown using graphite as the source for C. For higher Ge and C concentrations, Sb-surfactant mediation was found to be required to stabilize the surface morphology. The maximum value of substitutional C concentration, above which excessive generation of stacking fault defects caused polycrystalline and/or amorphous growth, was found to be approximately 2.4% in samples containing between 25 and 30% Ge. The fraction of substitutional C was found to decrease from roughly 60% by a factor of 0.86 as the Si1-x-yGexCy growth rate increased from 0.1 to 1.0 nm/s.

Original languageEnglish (US)
Pages (from-to)1937-1942
Number of pages6
JournalJournal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume16
Issue number4
StatePublished - Jul 1 1998

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ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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