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Ge/Si nanowire mesoscopic Josephson junctions

Nature Nanotechnology volume 1, pages 208–213 (2006)Cite this article

Abstract

The controlled growth of nanowires (NWs) with dimensions comparable to the Fermi wavelengths of the charge carriers allows fundamental investigations of quantum confinement phenomena. Here, we present studies of proximity-induced superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by superconducting leads. By using a top gate electrode to modulate the carrier density in the NW, the critical supercurrent can be tuned from zero to greater than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement in the radial direction, which results in stepwise increases in the critical current as a function of gate voltage. Transport measurements on these superconductor–NW–superconductor devices reveal high-order (n = 25) resonant multiple Andreev reflections, indicating that the NW channel is smooth and the charge transport is highly coherent. The ability to create and control coherent superconducting ordered states in semiconductor–superconductor hybrid nanostructures allows for new opportunities in the study of fundamental low-dimensional superconductivity.

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Figure 1: Schematic diagram and device image of a Ge/Si nanowire device.
Figure 2: Transport characteristics of Ge/Si nanowire above and below the superconducting transition temperature.
Figure 3: Multiple Andreev reflections in the Ge/Si nanowire device.
Figure 4: Gate-voltage dependence of critical current and normal conductance.

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Acknowledgements

We thank Y.J. Doh and J.U. Free for helpful discussions. M.T. acknowledges support from the National Science Foundation. R.M.W. acknowledges support of this work by DARPA-QuIST and the Nanoscale Science and Engineering Center at Harvard University. C.M.L. acknowledges support of this work by the Defense Advanced Research Projects Agency, Army Research Organization and NSF.

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Author notes

  1. A. Vidan

    Present address: MIT Lincoln Laboratory, Lexington, Massachusetts, 02420, USA

Authors and Affiliations

  1. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, 02138, Massachusetts, USA

    Jie Xiang & Charles M. Lieber

  2. Division of Engineering and Applied Sciences, Harvard University, Cambridge, 02138, Massachusetts, USA

    A. Vidan, M. Tinkham, R. M. Westervelt & Charles M. Lieber

  3. Department of Physics, Harvard University, Cambridge, 02138, Massachusetts, USA

    M. Tinkham & R. M. Westervelt

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  1. Jie Xiang
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  2. A. Vidan
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  3. M. Tinkham
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  4. R. M. Westervelt
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  5. Charles M. Lieber
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Contributions

J.X. and A.V. performed the experiments and analysed the data with help from M.T. All the authors discussed the results and co-wrote the manuscript.

Corresponding authors

Correspondence to R. M. Westervelt or Charles M. Lieber.

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The authors declare no competing financial interests.

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Xiang, J., Vidan, A., Tinkham, M. et al. Ge/Si nanowire mesoscopic Josephson junctions. Nature Nanotech 1, 208–213 (2006). https://doi.org/10.1038/nnano.2006.140

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