Resonant Raman scattering and atomic force microscopy of InGaAs/GaAs multilayer nanostructures with quantum dots
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The transition from two-dimensional (2D) pseudomorphic growth to the three-dimensional (3D) (nanoisland) growth in InxGa1−xAs/GaAs multilayer structures grown by molecular-beam epitaxy was investigated by atomic force microscopy, photoluminescence, and Raman scattering. The nominal In content x in InxGa1−xAs was varied from 0.20 to 0.50. The thicknesses of the deposited InxGa1−xAs and GaAs layers were 14 and 70 monolayers, respectively. It is shown that, at these thicknesses, the 2D-3D transition occurs at x ≥ 0.27. It is ascertained that the formation of quantum dots (nanoislands) does not follow the classical Stranski-Krastanov mechanism but is significantly modified by the processes of vertical segregation of In atoms and interdiffusion of Ga atoms. As a result, the InxGa1−xAs layer can be modeled by a 2D layer with a low In content (x < 0.20), which undergoes a transition into a thin layer containing nanoislands enriched with In (x > 0.60). For multilayer InxGa1−xAs structures, lateral alignment of quantum dots into chains oriented along the \([\overline 1 10]\) direction can be implemented and the homogeneity of the sizes of quantum dots can be improved.
KeywordsMicroscopy GaAs Atomic Force Microscopy Thin Layer Magnetic Material
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