Electronic and impurity states in triple quantum wells

A detailed theoretical study on spectra of donor-impurities in triple GaAs-(Ga,Al)As quantum wells in the presence of external electric and magnetic fields is presented. Impurity states are calculated, within the effective-mass approximation, by adopting a variational scheme in which ground and excited states are obtained simultaneously. Different geometrical confinement regimes for the impurities are considered and the effects of the induced field-confinement on the binding energies are analyzed. The impurity binding energy presents characteristic features determined fundamentally by the spatial distribution of the electronic wave function within the triple-well structure. We show that by changing the intensity of the external magnetic and electric field, a large spread in the range of the donor binding energy may be obtained. (C) 2001 Elsevier Science B.V. All rights reserved.