Low temperature magnetoresistance of a quasi-ballistic narrow wire confined by split metal gates

We have studied a size effect related to boundary scattering in two different types of quasi-ballistic, narrow wire system. Lateral confinement of a two dimensional electron gas, confined at the interface of a GaAs/AlGaAs heterojunction, was achieved alternatively through the use of a dry etch or by means of a pair of split metal gates. Clear differences in the magnitude of the size effect are observed between these two systems, which we explain in terms of the relative degree of specular and diffusive boundary scattering in the wires.