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Epitaxial Josephson junctions for superconducting qubits made by wafer-bonding

ORAL

Abstract

State-of-the-art transmons most often utilize Al/AlO x /Al Josephson junctions (JJs) even though the
amorphous AlO x is known to be defective and lossy. A scalable process to realize epitaxial JJs with low
loss barrier dielectrics could improve qubit performance beyond state-of-the-art; however, challenges in
materials integration have not yet been overcome. In this work, a wafer-bonding technique is used to
realize epitaxial JJ structures utilizing conventional semiconductors for the JJ dielectric. Semiconductors
and epitaxial superconductors are grown by molecular beam epitaxy on III-V semiconductor substrates
and bonded to low-loss substrates. Selective etching is used to remove the III-V substrate followed by
surface cleaning and superconductor regrowth, resulting in epitaxial Al/Semiconductor/Al tri-layers on
low loss substrates.

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Presenters

  • Anthony P McFadden

    UCSB, Dept. of Electrical Engineering, Univ. of California, Santa Barbara, CA, USA, University of California, Santa Barbara, Univ of California, Santa Barbara

Authors

  • Anthony P McFadden

    UCSB, Dept. of Electrical Engineering, Univ. of California, Santa Barbara, CA, USA, University of California, Santa Barbara, Univ of California, Santa Barbara

  • Corey Rae McRae

    NIST Boulder / CU Boulder, NIST, National Institute of Standard and Technology Boulder, National Institute of Standards and Technology Boulder

  • RUICHEN ZHAO

    National Institute of Standards and Technology Boulder, NIST, University of New South Wales

  • David Pappas

    NIST Boulder, National Institute of Standards and Technology Boulder, NIST, National Institute of Standards and Technology, National Institute of Standard and Technology Boulder, National Institute of Standards and Technology - Boulder

  • Chris J Palmstrom

    Materials Department, University of California, Santa Barbara, UCSB, Departments of Electrical and Computer Engineering and Materials, University of California, Santa Barbara, Dept. of Electrical Engineering, Univ. of California, Santa Barbara, CA, USA, Univ. of California, Santa Barbara, Electrical and Computer Engineering Department, University of California, Santa Barbara, University of California, Santa Barbara, IEE, UC Santa Barbara, University of California Santa Barbara, Univ of California, Santa Barbara, Electrical and Computer Engineering, University of California Santa Barbara, Materials and Electrical & Comp. Eng, University of California, Santa Barbara