  We have investigated the effect of the gate voltage on spin relaxation in an
Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As heterostructure. The study is motivated by a
recent proposal for a non-ballistic spin field effect transistor that utilizes
the interplay between the Rashba and the Dresselhaus spin-orbit interaction in
the device channel. The model, which utilizes real material parameters, in
order to calculate spin dynamics as a function of the gate voltage has been
developed. From the obtained results we define the efficiency of the spin
polarization and spin density modulation. The estimated modulation of the spin
polarization at room temperature is of the order of 15-20%. The results show
that the effect is not sufficient for device applications. However, it can be
observed experimentally by optical pulse-probe techniques.
