Ionized-impurity scattering in the strong-screening limit

We have developed a self-consistent multi-ion screening formalism which, unlike conventional treatments, explicitly assures that no electron state should contribute more than -e to the net charge screening the donors. A key finding is that formal consistency can be achieved only when neighboring ion potentials overlap somewhat. Ionized-impurity scattering in a semiconductor is therefore intrinsically a multi-ion process, and the tightly screened, isolated-impurity regime is unphysical. Temperature- and doping-dependent majority-carrier mobilities for uncompensated n-type Si, Ge, GaAs, and InP are recalculated using the ``multi-ion'' screening length. The correction to the mobility is often substantial (as much as a factor of 4), and in some regimes the agreement between theory and experiment is considerably improved.