Binding energies and photoionization cross-sections of donor and acceptor impurities in inverted core/shell ellipsoidal quantum dots: Effects of magnetic field, ellipsoid anisotropy and impurity position

摘要

Within the framework of the effective-mass approximation and by using a variational and perturbation approach, the binding energies and photoionization cross-sections of donor and acceptor impurities in an inverted core/shell ellipsoidal spherical quantum dot under an applied magnetic field have been studied. We have calculated the binding energies of both donor and acceptor impurities as a function of the core and shell sizes and shapes with different impurity positions under the applied magnetic field. In addition, the corresponding photoionization cross-section is calculated. Our results show that the binding energy of the acceptor impurity is larger than that of the donor impurity, and both of them with different impurity positions and quantum ellipsoid anisotropies will exhibit a nonmonotonic change. The peak value of the photoionization cross-section will reach a maximum with the increasing ratio R-1/R-2. It is found that the applied magnetic field can be an effective means of enhancing the photoionization cross-section of an impurity state in such core/shell quantum dot system.