Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 8: Postersitzung I: Supraleitung

TT 8.21: Poster

Monday, March 8, 2004, 14:30–19:00, Poster A

Andreev reflection at superconducting contacts to InGaAs/InP heterostructures — •I. E. Batov¹, Th. Schäpers², A. A. Golubov³, and A. V. Ustinov¹ — ¹Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen — ²Institut für Schichten und Grenzflächen, Forschungszentrum Jülich, 52425 Jülich — ³Faculty of Applied Physics, University of Twente, The Netherlands

Transport in hybrid devices consisting of superconductors (S) in contact with a two-dimensional electron gas (2DEG) is a subject of increasing interest in recent years. Novel transport phenomena arising due to Andreev reflection at the S/2DEG interface were predicted recently in such devices, such as magnetoconductance oscillations in the Quantum Hall regime, suppression of the Hall resistance near the S/2DEG interface, etc. To access the novel transport regime of interest, in most cases the high transparency of the S/2DEG contacts is essential. In this work, we report on the fabrication of highly transmissive contacts to the two-dimensional electron gas in InGaAs/InP heterostructures. As a superconductor NbN is used. High junction transmissivity was achieved by exploiting a process of sputtering a thin (10nm) Au interlayer followed by the deposition of the NbN electrode and rapid annealing at 400^∘C. We observed a decrease in the differential resistance of the junction with pronounced double-dip structure within superconducting energy gap. The effect of a magnetic field perpendicular to the plane of the 2DEG on the differential resistance of the interface was studied. Experimental data are analyzed within a model of ballistic SN-2DEG contact, based on the quasiclassical Green-function approach.