Influence of donor impurity on optical transitions in quantum dots

Few-electron systems have been studied by variational means for semiconduct or spherical quantum dots both with and without a donor center. It is shown that the pair (2e) and triple (3e) of electrons as well as the donor cente r with two (D-) and three (D2-) electrons can form several bound states if the range and depth of the confinement potential are sufficiently large. It is found that dipole-allowed optical-transition energies are nearly the sa me for the two groups of systems: {D-0 and D-} and {1e, 2e, 3e, and D2-}. F or D-0 and D-, the transition energies are significantly larger than for th e systems of the second group.