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Center for Nonlinear Studies |
An ability to control composition of semiconductor nano-structures opens an opportunity to engineer materials with desired electronic and optical properties. Modeling of the carriers interactions in such materials is a key issue for understanding and gaining experimental control of the photo-excited dynamics on the nano-meter lengthscale. In this talk, we present a model describing interactions between photoexcited carriers (electrons and holes) in semiconductor core/shell nano-structures. There are two major effects influencing the strength of the interactions such as quantum and dielectric confinements. The former is due to the carriers scattering at the potential wall produced by the nano-structure surface and a step-function potential at the core shell interface. This allows one to achieve localization of the carriers in the core and/or shell regions, as well as corresponds to different scaling of the carriers kinetic and Coulomb interaction energies with the nano-structure radius. The latter effect represents influence of the core/shell and shell/environment interface polarizations (image charges) on the carriers Coulomb coupling. We demonstrate that variation of the core/shell and shell/environment dielectric constant ratios can significantly affect the strengths and the sign of the Coulomb energy.