Hydrogenic impurity states in CdSe/ZnS and ZnS/CdSe core-shell nanodots with dielectric mismatch

Within the effective mass approximation we theoretically studied the electronic properties of CdSe/ZnS and ZnS/CdSe core-shell quantum dots surrounded by wide-gap dielectric materials. The finite element method is used to obtain the lowest impurity levels and the carrier spatial distribution within the dot. We found that in these zero-dimensional semiconductor structures the electron energy is sensitively dependent on the dielectric constants of the embedding and on the heterostructure geometry. The influence of polarization charges on the binding energy of hydrogenic impurities off-center located is also investigated. The results suggest that in dielectrically modulated nanodots the donor energy can be tuned to a large extent by the structure design, the impurity position and a proper choice of the dielectric media.