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2014 year, number 3


A. I. Nikiforov, V. A. Timofeev, S. A. Teys, and O. P. Pchelyakov
Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akadmika Lavrent’eva 13, Novosibirsk, 630090 Russia
Keywords: molecular beam epitaxy, silicon, germanium, solid solution, films, quantum dots, reconstruction, fast electron diffraction, activation energy, hut-islands, dome-islands


A kinetic diagram of Ge growth on Si is constructed by methods of fast electron diffraction and scanning electron microscopy. Activation energies of morphological transitions from twodimensional to three-dimensional growth and from hut-clusters to dome-type islands are determined. The curve of the 2D -3D transition has two segments that follow the Arrhenius law and refer to different mechanisms of two-dimensional growth: two-dimensional island mechanism in the temperature range of 300-525 ºC with the activation energy of −0.11 eV and step motion in the temperature range of 525-700 ºC with the activation energy of 0.15 eV. Transitions from hut-islands to dome-islands are also observed. The curve constructed for the hut-dome transition is approximated by two exponential segments that obey the Arrhenius law. The hut-dome transition activation energy is 0.11 eV in the temperature range of 350-550 ºC and 0.24 eV in the temperature range of 550-700 ºC. The maximum density of islands in the case of Ge growth on a Gex Si1 − x layer reaches 4 · 1011 cm−2. An increase in the composition leads to an increase in the density of Ge islands owing to a decrease in the length of migration of Ge adatoms on the GexSi1 − x surface, as compared to the case of Ge growth on Si. The periodicity N, which is manifested as a (2 × N ) superstructure, decreases during the reconstruction from 14 to 8 with increasing Ge content in the GexSi1 −x layer. An increase in thickness or temperature leads to a decrease in periodicity and testifies to Ge segregation; in this case, stress relaxation occurs, which reduces the Ge diffisivity.