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11 June 2003 Raman sudy of Ge quantum dots formed by submonolayer Ge coverages in Ge/Si superlattices
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Many attempts to create Si/Ge heterostructures with enhanced opto-electronic properties have been made since beginning of 90-th. Previously these hopes were connected with theoretical assumption that stressed ultra-thin Ge/Si superlattices (SLs) should have direct band gap structure. Recently, the great excitement of researchers was generated by promising optical properties of self-organizing Ge quantum dots (QDs) embedded in a Si matrix. Traditionally, Ge QDs are formed using relatively thick Ge deposition as a result of structural reconstruction of stressed system in order to minimize elastic energy (Stranski-Krastanow mechanism). It should be noted, that in this case there is always the wetting layer and the lateral sizes of Stranski-Krastanow QDs usually relatively high (tens of nanometers), which defines week vanishing of the wave-vector selection rules in the lateral direction. More recently, the mechanism of QDs formation using submonolayer (SML) insertions of a narrow-band semiconductor in a wide-band semiconductor matrix was proposed. In this case the average sizes of QDs are usually very small and its densities are very high. According to electron diffraction, electron microscopy and photoluminescence (PL) data the Ge QDs were formed in Ge/Si SLs with SML Ge insertions. Such Ge/Si heterostructures containing dense arrays of small Ge islands looks more promising for opto-electronic applications.
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Vladimir A. Volodin, D. A. Orehov, M. D. Efremov, V. A. Sachkov, B. A. Kolesov, N. D. Zakharov, V. A. Egorov, G. E. Cirlin, and P. Werner "Raman sudy of Ge quantum dots formed by submonolayer Ge coverages in Ge/Si superlattices", Proc. SPIE 5023, 10th International Symposium on Nanostructures: Physics and Technology, (11 June 2003);


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