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Armenian Journal of Physics=Ֆիզիկայի հայկական հանդես
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The brief overview of InAs-based III-V compound and Si/Ge semiconductor epitaxial strain-induced islands and quantum dots (QD) grown by Liquid Phase Epitaxy (LPE) and other techniques is presented. The main technological modes for fabrication of strain-induced islands and QDs are described. Our latest investigations and results for the growth of the self-assembled InAsSbP-based strain-induced islands and QDs on InAs(100) substrates by LPE technique are summarized. Here we show that such islands, as they decrease in size, are undergoing a shape transition. As the islands volume decreases, the following succession of shape transitions are detected: truncated pyramid, {111} facetted pyramid, {111} and partially {105} facetted pyramid, completely unfacetted “pre-pyramid”, which gradually evolve to semiglob and then to QD. The morphology, size, shape and composition of these objects are investigated by scanning electron microscope (SEM-EDAX–FEI Nova 600–Dual Beam), interconnected with the Focused Ion Beam (FIB) technique, energy dispersive X-Ray analysis (EDXA) technique and atomic force microscopy (AFM–TM Microscopes–Autoprobe CP). A critical size (~550 nm) of the InAsSbP-based strain-induced islands shape transformation from “pre-pyramid” to semiglobe is experimentally detected and, in addition, theoretically explained and calculated. Proposed theoretical approach has been also employed and tested for Si1-xGex model system islands grown on a Si(001) substrate. It is shown that for both materials theoretically calculated values of the critical size coincide with experimentally obtained data. EDAX measurements at the top and bottom’s angles of the InAsSbP quaternary pyramids and lattice mismatch ratio calculations have been performed. These measurements showed that the strength at the top of pyramids is lower than at the bottom’s angles, and that the islands size becomes smaller when the lattice mismatch decreases. The LPE technological conditions for the fabrication of quaternary InAsSbP QDs on InAs(100) substrate are described. The QDs average density ranges from 5 to 7×109 cm-2, with heights and widths dimensions from 0.7 nm to 25 nm and 20 nm to 80 nm, respectively. The Gaussian distribution of QD’s amount versus to their average diameter has been experimentally detected. The transmission spectra at room temperature of an unencapsulated InAsSbP QDs by the Fourier-Transform Infrared Spectrometry (FTIR–Nicolet/NEXUS) were investigated. The displacement of absorption edge toward the long wavelength region from λ = 3.44 μm (for InAs test sample) to λ = 3.85 μm (for InAs with QDs) has been detected.
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