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

Research output: Contribution to journalArticle

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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 1998

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Molecular beam epitaxy
Silicon carbide
silicon carbides
Surface morphology
Heterojunctions
Surface active agents
molecular beam epitaxy
Transmission electron microscopy
Defects
mediation
Superlattices
Stacking faults
Rutherford backscattering spectroscopy
Backscattering
Secondary ion mass spectrometry
Chemical analysis
Spectrometry
backscattering
Graphite
Diffraction

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Physics and Astronomy (miscellaneous)
  • Surfaces and Interfaces

Cite this

Stabilizing the surface morphology of Si1-x-yGexCy/Si heterostructures grown by molecular beam epitaxy through the use of a silicon-carbide source. / Croke, E. T.; Vajo, J. J.; Hunter, A. T.; Ahn, C. C.; Chandrasekhar, D.; Laursen, T.; Smith, David; Mayer, J. W.

In: Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, Vol. 16, No. 4, 07.1998, p. 1937-1942.

Research output: Contribution to journalArticle

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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.",
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