Origin of positive magnetoresistance in small-amplitude unidirectional lateral superlattices

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We report quantitative analysis of positive magnetoresistance (PMR) for unidirectional-lateral-superlattice samples with relatively small periods (a=92-184 nm) and modulation amplitudes (V₀=0.015-0.25 meV). By comparing observed PMR's with ones calculated using experimentally obtained mobilities, quantum mobilities, and V₀'s, it is shown that contribution from streaming orbits (SO) accounts for only small fraction of the total PMR. For small V₀, the limiting magnetic field Bₑ of SO can be identified as an inflection point of the magnetoresistance trace. The major part of PMR is ascribed to drift velocity arising from incompleted cyclotron orbits obstructed by scatterings.