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supercurrent is completely suppressed. In contrast to wide S/semiconductor/S Josephson junctions, 27 no Fraunhofer-type interference pattern of I c ( B ) is ob- served. The absence of a magnetic interference pattern in SNS structures was first observed by Anger et al. 28 and theoretically explained by Hammer et al. 16 and Cuevas and Bergeret. 17 The reason for the monotonous decay of I c is that for junctions with a width smaller than the magnetic length ξ B the magnetic field acts as a pair- 

∗ Current address: Physics Department University of Cali- fornia Santa Barbara, 93106 Santa Barbara CA, USA † 

Nanoelektronik, Technische Fakult¨ at, Christian-Albrechts- Universit¨ at zu Kiel, 24143 Kiel, Germany ‡ 

Electronic address: th.schaepers@fz-juelich.de 1 

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T. Sch¨ apers, Superconductor/Semiconductor Junctions , vol. 174 of Springer Tracts on Modern Physics (Springer- Verlag, Berlin Heidelberg, 2001). 3 

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C. Thelander, P. Agarwal, S. Brongersma, J. Eymery, L. Feiner, A. Forchel, M. Scheffler, W. Riess, B. Ohlsson, 

breaking factor. Indeed at the field of 0.16 T where the first minimum at Φ$_{0}$ is expected in the Fraunhofer interference pattern the magnetic length ξ B is as large as 110 nm and thus comparable to the junction width. For sample B a similar dependence of I c on B is ob- served with a full suppression of I c at 0.2 T. By using the model of Hammer et al. 16 for the the case of low transparent junctions we calculated the expected depen- dence of I c on B for E ∗ Th = 0 . 15 meV. As can be seen in Fig. 3(b), a reasonable agreement between experiment and theory is obtained. The same is true for sample B with E ∗ Th = 0 . 7 meV [cf. Fig. 3(b), inset]. A possi- ble reason for the discrepancy between the experimental values and theoretical curves might be that in our InN nanowires the current flows mainly in the surface accu- mulation layer, which leads to an inhomogeneous current distribution. 

In summary, superconducting Nb/InN-nanowire/Nb junctions with large critical currents up to 5.7 µ A and large I c R N products up to 0.44 mV have been fabricated. Owing to the small width of nanowires a monotonous decrease of I c with B was observed, since in this case the magnetic field is the main pair breaking factor. The present results suggest that Nb/InN-nanowire/Nb struc- tures are well suited for fundamental research and appli- cation in nano-scaled Josephson junction-based devices. 

We are grateful to A. A. Golubov (Twente Univer- sity, The Netherlands) and V. V. Ryazanov (Institute of Solid State Physics RAS, Chernogolovka) for fruitful discussions and H. Kertz for support during the measure- ments. I.E.B. acknowledges the Russian Foundation for Basic Research: project RFBR 09-02-01499 for financial support. 

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