Hydrogenic impurity states in the spherical CdSe/ZnS/CdSe nanoheterostructure

Abstract

To study the optical properties of a medium with an ensemble of quantum dots (QDs) it is necessary to clarify properties of a single dot. We investigated the influence of increasing core and shell size on the states energy for a single spherical CdSe/ZnS/CdSe core–shell QD, in the presence of the hydrogenic impurity located in the center. Investigated nanoheterosystem behaves as quantum antidot for particular geometry. Calculations of the hydrogenic impurity discrete states in the spherical semiconductor multilayered nanoheterosystem are performed under effective mass approximation by assuming a spherically symmetric confining potential of finite depth. On the basis of the analytical solutions of the Scrödinger and Poisson equations for QD with hydrogenic impurity located in the center, energy of discrete states and corresponding wave functions for CdSe/ZnS/CdSe QD are determined. Energies of 1s, 2s, 3s, 2p, 3p, and 3d states, and radial probabilities, that illustrate spatial charge distribution, are presented in this paper. Behavior of 1s is the most prominent. For small core radius 1s orbital expands out of the dot with energy below the bottom of the outer material conduction band i.e. core material in this particular case. When core radius increases energy increases and at characteristic core dimension, 1s orbital contracts into the core region and the ground state energy decreases till it reaches constant value, characteristic for core material.