Screening of Donors in GaAs/Ga1_xAlxAs as Quantum Dots.

We have carried out variation al model calculations of the binding energy of a screened donor in a spherical GaAs/Gal_x~As quantum dot as a function of the quantum dot radius. We have found that the effect of screening on the binding energy of the donor becomes more pronounced as the radius of the quantum dot decreases. This behavior is similar to that obtained earlier in model calculations of the binding energy of a donor in a quantum well, or in a quantum-well wire