The effect of the electric field on the photoionization cross-section

The effect of the electric field on the donor impurity is investigated in the case of a spherical conduction band with the use of a variational procedure. An analytical expression for the photoionization cross-section as a function of photon energy within the effective mass approximation of an impurity atom in an applied field was obtained. The effect of central cell correction by means of a semiempirical short-range potential is taken into account. It has been found that the binding energy and the spectral dependence of the cross-section are very sensitive to the electric field, the shape of the impurity potential and their combined effect.