Superconductor-semiconductor interaction effects in mesoscopic hybrid structures

We have studied transport in mesoscopic superconductor-semiconductor hybrid structures consisting of two-dimensional arrays of micrometer-sized niobium dots deposited on high-mobility InAs:GaSb quantum wells. The grating arrays were designed to have a dot size and spacing of 3, 1.5, and 1 μm, so as to be smaller than the electron mean free path of ∼5 μm. At low temperatures all the structures show clear evidence of Andreev reflection while the two smaller period samples also exhibit a proximity-induced superconducting phase. We present measurements 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 nonuniform flux penetration around the superconducting dots.