We have theoretically studied the electronic structure of Si δ-doped GaAs inserted into an infinite quantum well as dependent on the applied electric field. For the uniform distribution we have investigated the influence of the electric field on the donor distribution thickness as different from other authors. The present method is based on a self-consistent solution of the Schrödinger and Poisson equations. From our calculations, we have seen that a high applied electric field is significantly changed the subband structure of the δ-doped GaAs and the change of the electronic properties as dependent on the applied electric field is more pronounced at wide doping thickness. The high electric fields can induce a spatial separation between confined electrons and ionized dopants in the δ-doped GaAs structure resulting in enhanced free carrier mobility in semiconductor devices.