ELECTRON MOMENTUM RELAXATION-TIME AND MOBILITY IN A FREESTANDING QUANTUM-WELL

Kinetic characteristics of the electron transport in a free-standing q uantum well are studied theoretically. The quantization of acoustic ph onons in a free-standing quantum well is taken into account and electr on interactions with confined acoustic phonons through the deformation potential are treated rigorously. The kinetic equation for the electr on distribution function is solved numerically for nondegenerate as we ll as degenerate electron gases and the electron momentum relaxation t ime and the electron mobility are obtained. At high lattice temperatur es the electron momentum relaxation time is very similar to that obtai ned in the test particle approximation. Its dependence on the electron energy has steps which occur at the threshold energies for the dilata tional phonons because an additional electron scattering by the corres ponding acoustic phonon becomes important. The first mode makes the ma in contribution to the electron scattering, the contributions of the z eroth and the second modes are also important, the third and the highe r modes practically unnoticeable for the studied electron concentratio ns and quantum well width. At lattice temperatures lower than the ener gy of the first dilatational acoustic mode the electron momentum relax ation time dependence on energy has additional peaks (in comparison wi th the test particle approximation) associated with electron scatterin g by several lowest acoustic phonon modes. These peaks occur near the Fermi energy in the degenerate case and in the energy range of the fir st dilatational modes in the nondegenerate case. They are especially p ronounced for the degenerate electron gas. The temperature dependence of the electron mobility is similar to that described by the Bloch-Gru neisen formula, however we obtained a smaller negative exponent in the low temperature region. (C) 1995 American Institute of Physics.