Shot-noise and conductance measurements of transparent superconductor /   two-dimensional electron gas junctions
  We have measured the conductance and shot-noise of superconductor-normal metal (S-N) junctions between a Niobium (Nb) film and a 2-dimensional electron gas (2DEG), formed in an InAs-based semiconductor heterostructure. Adjacent to the junction, the 2DEG is shaped into a submicrometer beam-splitter. The current shot-noise measured through one arm of the beam-splitter is found to be enhanced due to Andreev reflection. Both noise and conductance measurements indicate that the Nb-2DEG interface is of high quality with a transparency approaching approx. 60-70 %. The present device can be seen as a quasi-ballistic S-N beam-splitter junction. 
B.-R. Choi, A. E. Hansen, T. Kontos, C. Hoffmann, S. Oberholzer, W.   Belzig, C. Schoenenberger, T. Akazaki, and H. Takayanagi