MAGNETORESISTANCE IN A BACK-GATED SURFACE SUPERLATTICE

We study a surface superlattice structure, consisting of a two dimensi onal electron gas (2DEG) with a periodic array of Schottky gates on th e surface and an additional back gate, which independently controls th e 2DEG density. We use several independent features in the magnetoresi stance to dele;mine the magnitude V of the periodic potential induced in the 2DEG, and its dependence on the gate voltages; We obtain a syst ematic quantitative picture of V, which is generally in good agreement with theoretical expectations. However our density dependence cannot be accounted for within the usual picture of static screening in a 2DE G.