We have theoretically investigated the diffusion of donor impurities of single Si delta-doped GaAs inserted into a quantum well at T=0 K. The spread of the impurities is taken into account in three different models: (i) a uniform distribution, (ii) a triangular distribution and (iii) a nonuniform distribution. In this article, the nonuniform distribution is different from the Gaussian distribution used by other authors. The electronic structures were calculated by solving the Schrodinger and Poisson equations self-consistently. We also found the confining potential, the charge density, the subband energies, the subband occupations and the Fermi energy. In this study, we have seen that the electronic structures are quite sensitive to the type of donor distribution when the thickness of the donor distribution (Deltaz) is large. (C) 2002 American Institute of Physics.