  We study high-field spin transport of electrons in a quasi one-dimensional
channel of a $GaAs$ gate controlled spin interferometer (SPINFET) using a
semiclassical formalism (spin density matrix evolution coupled with Boltzmann
transport equation). Spin dephasing (or depolarization) is predominantly caused
by D'yakonov-Perel' relaxation associated with momentum dependent spin orbit
coupling effects that arise due to bulk inversion asymmetry (Dresselhaus spin
orbit coupling) and structural inversion asymmetry (Rashba spin orbit
coupling). Spin dephasing length in a one dimensional channel has been found to
be an order of magnitude higher than that in a two dimensional channel. This
study confirms that the ideal configuration for a SPINFET is one where the
ferromagnetic source and drain contacts are magnetized along the axis of the
channel. The spin dephasing length in this case is about 22.5 microns at
lattice temperature of 30K and 10 microns at lattice temperature of 77 K for an
electric field of 2 kV/cm. Spin dephasing length has been found to be weakly
dependent on the driving electric field and strongly dependent on the lattice
temperature.
