A contrasting situation is provided by electrons trapped in a GaAs quantum well. Suppose that the well is 10 nm wide with 3 x 1015m-2 electrons, which might arise from remote doping (undoped well) or from a uniform density of donors in the well. Use the wave function of an infinitely deep well to calculate the electrostatic potential from the electrons and show that its effect on the confining potential is small for both types of doping. Continue by finding the change in energy of the bound state with perturbation theory.