INVESTIGATION OF NB CONTACTS TO A GAINAS INP HETEROSTRUCTURE/

Lateral contacts between a high-mobility 2-dimensional electron gas (2 DEG) and superconducting Nb have been prepared by etching down the het erostructure and depositing Nb on the mesa from the side. A second kin d of contact has been achieved by depositing the Nb on top of the hete rostructure contacting the 2DEG through a 60 nm thick barrier of Ga0.4 7In0.53As. Both kinds of contacts show a pronounced nonlinearity in th e differential resistance due to the superconducting energy gap. The I -U characteristics of the different contact configurations are compare d and discussed in terms of the interplay between Andreev and ordinary reflection processes at both kinds of Nb-2DEG interfaces.