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Information × Registration Number 0214U006087, 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 In Germanium-Silicon structures, effects of interaction between excitons are more essential, than for dipolar excitons in AlGaAs/GaAs/AlGaAs heterostructures. For investigation of exciton-exciton phenomena, a wave function of the exciton is needed. Literature data are not sufficient concerning this matter, moreover the data from different authors are contradictory. The wave function and the bounding energy of the ground state of the exciton is calculates in type-II quantum well Si/Si1-xGex/Si, taking into account several valleys of band spectrum of an electron in Silicon and anisotropy of effective masses of charge careers. It is shown that an hole in the given structure is strong-localized in quantum well, but shape, localization rate of the wave function and the rate of its penetration into barrier layer sufficiently depend on the parameters of the structure. The exciton energy is found to decrease with the growth of the quantum well width and with Germanium concentration enlargement in quantum well layer. The theory of the condensed islands formation is composed for 2D system at the constant pumping for particles with finite lifetime, depending on parameters, which characterize the interaction between exctions. The theory is based on solving the kinetic equations for the condensed phase system with n particles and the diffusion equation outside the condensed phase. The considered phases exist at the presence of an external irradiation (the pumping). Thus, the system are non-inequilibrium and this leads to the properties dependence on the kinetic characteristics of the system, for example, on the exciton diffusion coefficient. The theory is applicable for dipolar exciton condensation and for electron-hole pairs. Due to finite lifetime of the particles, the sizes of the condensed phase are restricted, and the condensed phase regions exist in the shape of the islands in the quantum well. The threshold values of the islands formation are found, and also the radii dependence on the pumping, the bounding energy for an electron-hole pair with an island, on the temperature and on the parameters of the exciton-exciton interaction (especially, on the dipole-dipole repulsion) are investigated. Numerical calculations are fulfilled for the systems with the parameters, which are typical for Germanium-Silicon nanostructures. The radii in SiGe compounds are bigger than ones in AlGaAs heterostructures. It is sown, that the threshold value of the island creation is strongly decreases with growth of the bounding energy of the electron-hole pair in an island at low energy values, and with further energy growth this decrease slows down. The phase diagrams "a critical value of the pumping - the temperature" is plotted. The threshold value of the condensed phase formation is found to increase with increasing the dipole-dipole interaction between excitons. Product Description popup.authors Буник Олексій Олександрович Верцімаха Ганна Віталіївна Михайловський Віталій Валерійович Чернюк Андрій Аркадійович popup.nrat_date 2020-04-02 Close