LIMITED POTENTIAL MODEL FOR UNSCREENED IONIZED IMPURITY SCATTERING INMULTIPLE-QUANTUM-WELL STRUCTURES

Unscreened ions are frequently the dominant source of carrier scatteri ng, in particular for electrons in barriers of quantum wells. A new mo del is introduced for this mechanism in which the Coulomb potential is limited to half the distance between nearest ions. Previously this me chanism was analyzed using the Conwell-Weisskopf (CW) model where, in order to avoid the divergence at low scattering angles, a critical ang le 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 temperatur es the results differ by an order of magnitude. Measurements taken at 20 K and 77 K verify the LP approximation. (C) 1998 Academic Press Lim ited.