Superconductor-semiconductor junctions with InAs/Al(Ga)Sb quantum wells

We report on the fabrication and the electrical characterization of the superconductor (Pb alloy)-semiconductor (InAs) junctions. Submicron scale superconducting weak link devices were fabricated on InAs/AlGaSb. The contact resistance of sequentially evaporated In/Pb/In and Au/Pb/In electrodes were reduced to be 0.2 fl mm. The differential resistance of the weak link devices measured between 2.6 and 5.5 K revealed multiple Andreev reflection indicating ballistic carrier transport in the superconductor-semiconductor junction. The modulation of conductance across the superconducting electrodes has been demonstrated on the Pb alloy-InAs structure for the first time by applying gate bias voltages at 4.2 K.