Abstract
The phonon modes of self-assembled Ge/Si quantum dots grown by molecular-beam epitaxy in an apparatus integrated with a chamber of the scanning tunneling microscope into a single high-vacuum system are investigated using Raman spectroscopy. It is revealed that the Ge-Ge and Si-Ge vibrational modes are considerably enhanced upon excitation of excitons between the valence band Λ3 and the conduction band Λ1 (the E 1 and E 1 + Δ1 transitions). This makes it possible to observe the Raman spectrum of very small amounts of germanium, such as one layer of quantum dots with a germanium layer thickness of ≈10 Å. The enhancement of these modes suggests a strong electron-phonon interaction of the vibrational modes with the E 1 and E 1 + Δ1 excitons in the quantum dot. It is demonstrated that the frequency of the Ge-Ge mode decreases by 10 cm−1 with a decrease in the thickness of the Ge layer from 10 to 6 Å due to the spatial-confinement effect. The optimum thickness of the Ge layer for which the size dispersion of quantum dots is minimum is determined.
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Original Russian Text © I.V. Kucherenko, V.S. Vinogradov, N.N. Mel’nik, L.V. Arapkina, V.A. Chapnin, K.V. Chizh, V.A. Yur’ev, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 10, pp. 1888–1894.
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Kucherenko, I.V., Vinogradov, V.S., Mel’nik, N.N. et al. The role of interdiffusion and spatial confinement in the formation of resonant raman spectra of Ge/Si(100) heterostructures with quantum-dot arrays. Phys. Solid State 50, 1970–1977 (2008). https://doi.org/10.1134/S1063783408100302
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DOI: https://doi.org/10.1134/S1063783408100302