Signatures of Induced Superconductivity in NbTi Contacted InAs Quantum Wells

ORAL

Abstract

We have studied electrical transport through InAs quantum wells grown by MBE with unannealed superconducting NbTi contacts deposited \textit{ex-situ} and patterned by optical photolithography. Characterization of the InAs 2DEG's without superconducting contacts yields typical mobilities greater than 100,000 cm$^{\mathrm{2}}$/Vs at a density of 4e11 cm$^{\mathrm{-2}}$. NbTi-InAs-NbTi (SNS) and NbTi-InAs (SN) devices with dimensions greater than 1 \textmu m are fabricated using optical lithography. Although the dimensions of the fabricated SNS devices are too large to observe a supercurrent, signatures of superconductivity induced in the InAs are present. We observe two superconducting critical temperatures: one of the NbTi leads (T$_{\mathrm{c\thinspace }}$\textasciitilde 8K), and a second (T$_{\mathrm{c}}$ \textless 4.5K) attributed to superconductivity induced in the InAs channel. dI/dV vs V spectroscopy on SNS junctions below the second critical temperature shows a conductance maximum at zero applied voltage while conductance minima appear at finite bias voltage which is attributed to the presence of an induced superconducting gap in the InAs quantum well.

*This work has been supported by Microsoft research

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Authors

  • Anthony P. McFadden

    • ECE Department, University of California - Santa Barbara
    • Department of Electrical and Computer Engineering, University of California at Santa Barbara
    • Department of Electrical and Computer Engineering, Univ of California, Santa Barbara

  • J Shabani

    • Physics Department, City College of New York
    • Physics Department, CCNY

  • Borzoyeh Shojaei

    • Materials Department, University of California - Santa Barbara

  • Joon Sue Lee

    • California NanoSystems Institute, University of California - Santa Barbara

  • Chris Palmstrøm

    • ECE and Materials Department, University of California - Santa Barbara