  The model of a spherical quantum dot with several donor impurities on its
surface is suggested. The electron energy spectra are studied as a function of
the quantum dot radius and the number of impurities. Several cases of the
location of impurities on the quantum dot surface are considered. The plane
wave functions method has been applied to calculate the electron energy
spectrum. The splitting of electron energy levels is analyzed in the cases of
different number of impurities. It is shown that the electron energy splitting
depends on both the number of impurities on the surface and on their location.
The electron binding energy is defined too.
