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Information × Registration Number 0214U006088, 0113U002800 , R & D reports Title Collective phenomena and spatial self-organization in the system of diplolar excitons in quasi two-dimensional germaium-silicon heterostructures popup.stage_title Head Sugakov Volodymyr, Registration Date 11-02-2014 Organization Institute For Nuclear Research Of National Academy Of Sciences Of Ukraine popup.description2 Quantum-mechanical calculations of the exciton energy are fulfilled for three types of Silicon-Germanium heterostructures: 1) the heterostructures Si/Si1-xGex /Si with thin strained layer of Si1-xGex, at which a straight exciton is created without constant dipole moment (structure I); 2) the heterostructures with wide quantum well, in which the state electron distribution at one or another side of the well (structure II, with the excitons with dipole moment are created); 3) the heterostructures, in which besides the layer Si1-xGex, the layers of Silicon, put into Si1-xGex layers, exist and in such a way the quantum well is created (structure III). For these structures, the dependence of the exciton energy on the quantum well width and Germanium concentration in the quantum well layer is obtained. For the structures II, the values of the dipole moment of the exciton is found, its dependence on the parameters of the external electric field and the estimations of the exciton dipole-dipole interaction. The process of the exciton condensation is investigated in Lifshits-Slyozov model, which is generalized for the particles of a finite lifetime. The threshold phenomena at the exciton condensation are studied. The phase diagram "the threshold pumping - the temperature" is plotted. It is shown, that the threshold of the condensed phase creation at low temperatures significantly depends on long-range dipole-dipole interaction between excitons. The processes of the exciton condensation and electron-hole liquid creation are significantly affected by non-equilibrium of the system. The non-equilibrium is caused be the finite lifetime of excitons and the pumping presence. The finite lifetime of excitons leads to finite sizes of the exciton phase islands. In two-dimensional system the condensed phases exist in the shapes of islands. Due to finite lifetime, strong correlation between the location of separate islands exists. In the model of self-consistent field for the system of islands, which interact through the exciton concentration field, the sizes of condensed phase islands are found, the concentration of islands (i.e., average distance between them) and the intensity of the light irradiation by islands depending on the intensity of the pumping and the temperature. It is shown that the average radius of the condensed phase island enlarges with the pumping growth by nearly linear low at the fixed temperature and slowly changes with the temperature at the fixed pumping; the islands concentration does not almost depend on the pumping at the fixed temperature and decreases with the temperature growth at the fixed pumping. The irradiation intensity at the fixed temperature grows with the pumping at the rate, which slightly exceeds a linear low, and decreases with pumping growth at the fixed pumping. The electron-hole pairs distribution is investigated in the quantum well at the irradiation of the limited part of the well. At the pumping values, which are bigger than the threshold one, islands of the condensed phase arises in the system, and the spatial distribution of them depends on the shape of the irradiated areas and mutual correlation. At great pumping values, the continuous condensed phase emerges in the irradiated areas. The generated structures are the result of self-organization processes in non-equilibrium systems. The impulse excitation of the quantum well, at which the impulse of the exciton condensed phase or of the electron-hole liquid is formed. For the impulse of the condensed phase, the maximal value of the electron-hole pairs density remains the constant during the lifetime of the pairs. Meanwhile, the impulse created by the exciton system in the gaseous phase fades away very fast. These impulses are proposed to use for the transfer of the information, which is controlled by the laser, in microsystems. Product Description popup.authors Буник Олексій Олександрович Верцімаха Ганна Віталіївна Михайловський Віталій Валерійович Чернюк Андрій Аркадійович popup.nrat_date 2020-04-02 Close