Investigation of Nb contacts to a GaInAs/InP heterostructure
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Lateral contacts between a high-mobility 2-dimensional electron gas (2DEG) and superconducting Nb have been prepared by etching down the heterostructure and depositing Nb on the mesa from the side. A second kind of contact has been achieved by depositing the Nb on top of the heterostructure contacting the 2DEG through a 60 nm thick barrier of Ga0.47In0.53As. Both kinds of contacts show a pronounced nonlinearity in the differential resistance due to the superconducting energy gap. The I-U characteristics of the different contact configurations are compared and discussed in terms of the interplay between Andreev and ordinary reflection processes at both kinds of Nb-2DEG interfaces.