Limited potential model for unscreened ionized impurity scattering in multiplequantum-well structures

Unscreened ions are frequently the dominant source of carrier scattering, in particular for electrons in barriers of quantum wells. A new model is introduced for this mechanism in which the Coulomb potential is limited to half the distance between nearest ions. Previously this mechanism was analyzed using the Conwell-Weisskopf (CW) model where, in order to avoid the divergence at low scattering angles, a critical angle is introduced below which scattering is prohibited. As such, CW is not suitable for quantum particles. The momentum relaxation times and mobilities derived from the limited potential (LP) model coincide with the results of CW for larger energies. At low energies and temperatures the results differ by an order of magnitude. Measurements taken at 20 K and 77 K verify the LP approximation.