Large positive magnetoresistance in a high-mobility two-dimensional electron gas: Interplay of short- and long-range disorder

We have observed a large positive quasiclassical magnetoresistance (MR) in a high mobility two-dimensional electron gas in an AlGaAs∕GaAs heterostructure. The magnetoresistance is nonsaturating and increases with magnetic field as Δρₓₓ~B^α0.3em0ex(α=0.9-1.2). In antidot lattices a nonmonotonic MR is observed. We show that in both cases this MR can be qualitatively described in terms of the theory recently advanced by Polyakov et al. [Phys. Rev. B 64, 205306 (2001)]. Their prediction is that the behavior we observe may be the consequence of a concurrent existence of short- and long-range scattering potentials.