Resonance states of quantum dots with D-0 centers in a magnetic field

We study the influence of a magnetic field on the resonant states of multis hell nanocrystals with a neutral donor impurity center. The nanocrystals st udied are composed of an internal well-acting core, coated with a barrier-a cting middle shell and a thick external cap. The donor impurity is located in the center of the structure. The calculations are performed within the o ne-band spherical effective mass approximation. We show that: (i) as in the undoped structure (Bylicki and Jaskolski, Phys. Rev. B 60 (1999) 15 924) t he magnetic field turns near-threshold resonant states into bound states. ( ii) Contrary to the bound states of the donor, the energy of the resonance- originating state changes rapidly even for a weak magnetic field, leading t o significant changes in the bound energy spectrum. For small nanocrystals the charge density of the donor ground state is localized in the outer cap. When the field is on, the resonant state binds and turns into the ground s tate with a non-negligible density inside the dot core. This effect is inve stigated for several symmetries and quantum dot structures. (C) 2001 Elsevi er Science Ltd. All rights reserved.