The effect of acoustic phonon confinement on the momentum and energy relaxation of hot carriers in quantum wires

The momentum and energy relaxation rates associated with electron-acoustic phonon interaction in a free-standing rectangular GaAs quantum wire have been calculated taking into account confined and interface phonon modes. Phonon confinement has two major consequences: (i) it increases relaxation rates by several orders of magnitude, and (ii) it increases the ratio of absorption to emission processes in narrow intervals of energy thereby making the energy relaxation rate in these intervals negative. An external magnetic field always decreases the momentum relaxation rate (thus increasing the carrier mobility) even though the scattering rate (the inverse of the quasi-particle lifetime) may increase or decrease depending on whether the interaction is polar (piezoelectric) or non-polar (deformation potential).