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Characterization of Coherent Si1−xGex Island Superlattices on (100) Si

Published online by Cambridge University Press:  01 February 2011

Jean-Marc Baribeau ,
Xiaohua Wu ,
Marie-Josée Picard  and
David J. Lockwood
Jean-Marc Baribeau
Affiliation:
[email protected], National Research Council Canada, Institute for Microstructural Sciences, 1200 Montreal Road, Building M50, Ottawa, K1A 0R6, Canada
Xiaohua Wu
Affiliation:
[email protected], National Research Council Canada, Institute for Microstructural Sciences, 1200 Montreal Rd, Ottawa, K1A 0R6, Canada
Marie-Josée Picard
Affiliation:
[email protected], National Research Council Canada, Institute for Microstructural Sciences, 1200 Montreal Rd, Ottawa, K1A 0R6, Canada
David J. Lockwood
Affiliation:
[email protected], National Research Council Canada, Institute for Microstructural Sciences, 1200 Montreal Rd, Ottawa, K1A 0R6, Canada
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Abstract

We examine the nanostructural properties of Si/Si1−xGex island superlattices with 0.37 < x < 0.56 grown at 620-640 °C by molecular beam epitaxy. Analytical transmission electron microscopy (TEM) shows that during growth Ge atoms migrate towards the center of the large islands to maintain epitaxial growth and that the most regular structures are obtained at higher Ge composition when the built-in strain is also higher. High-resolution x-ray reciprocal space mapping shows that these heterostructures remain pseudomorphic and that the undulations are aligned along [010] directions and exhibit a long-range coherence and vertical correlation as revealed by the presence of strong satellites in a wave vector direction parallel to the surface. Raman spectra of these samples exhibit the usual Ge-Ge, Si-Ge and Si-Si vibrational modes. When compared with planar Si/Si1−xGex superlattices the Ge-Ge and Si-Ge Raman peaks are shifted to lower frequencies indicating an average alloy composition that is approximately x = 0.1 less than the nominal values, which is in general agreement with analytical TEM.

Keywords

epitaxynanostructureGe
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 958: Symposium L – Group IV Semiconductor Nanostructures—2006 , 2006 , 0958-L10-32
Copyright
Copyright © Materials Research Society 2007

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References

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