SUPERCONDUCTOR-SEMICONDUCTOR INTERACTION EFFECTS IN MESOSCOPIC HYBRIDSTRUCTURES

We have studied transport in mesoscopic superconductor-semiconductor h ybrid structures consisting of two-dimensional arrays of micrometer-si zed niobium dots deposited on high-mobility InAs:GaSb quantum wells. T he grating arrays were designed to have a dot size and spacing of 3, 1 .5, and 1 mu m, so as to be smaller than the electron mean free path o f similar to 5 mu m. At low temperatures all the structures show clear evidence of Andreev reflection while the two smaller period samples a lso exhibit a proximity-induced superconducting phase. We present meas urements of the differential resistance at different temperatures and magnetic fields. For fields greater than 0.3 T, different features are observed in the differential resistance which we attribute to nonunif orm flux penetration around the superconducting dots.