Width dependence of quantum lifetimes in GaAs/AlxGa1-xAs heterostructures

We have studied the channel width dependence of quantum lifetimes tau(q) (or equivalently the quantum rhobilities (mu(q) = e tau(q)/m*) for samples with the widths w of 2-50 mu m fabricated from three GaAs/AlxGa1-xAs wafers. mu(q) estimated from the amplitude of Shubnikov-de Haas oscillations is found not to be affected by the asymmetry of Shubnikov-de Haas peaks and the boundary scattering observed in narrow samples. However, the two- to one-dimensional crossover occurring at w < L(T) (thermal diffusion length) leads to the reduction of mu(q). In addition, we have also carried out similar measurements with the sample illuminated with a red light-emitting diode. The results obtained from the illuminated samples confirm those from the unilluminated samples.