EXPERIMENTAL-DETERMINATION OF THE QUASI-PARTICLE DECAY LENGTH XI(QP) IN A DIFFUSIVE SUPERCONDUCTING QUANTUM-WELL

We have experimentally investigated the electronic transport propertie s of an AlSb/InAs/AlSb quantum well, where part of the AlSb top layer has been replaced with a superconducting Nb strip. By doing a transmis sion experiment underneath the Nb strip and comparing the results with a model based on diffusive transport, with some of the injected elect rons being Andreev reflected into holes, we can estimate the quasipart icle decay length, xi(qp) similar to 50 nm, in the Nb-InAs superconduc ting quantum well. This decay length corresponds to an interface trans parency of T-SIN = 0.5 between the Nb and InAs. The observed voltage d ependence cannot entirely be understood within the presented model.