Anodic oxidation of epitaxial superconductor-semiconductor hybrids

Asbjørn C. C. Drachmann, Rosa E. Diaz, Candice Thomas, Henri J. Suominen, Alexander M. Whiticar, Antonio Fornieri, Sergei Gronin, Tiantian Wang, Geoffrey C. Gardner, Alex R. Hamilton, Fabrizio Nichele, Michael J. Manfra, and Charles M. Marcus
Phys. Rev. Materials 5, 013805 – Published 25 January 2021
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Abstract

We demonstrate a new fabrication process for hybrid semiconductor-superconductor heterostructures based on anodic oxidation (AO), allowing controlled thinning of epitaxial Al films. Structural and transport studies of oxidized epitaxial Al films grown on insulating GaAs substrates reveal spatial nonuniformity and enhanced critical temperature and magnetic fields. Oxidation of epitaxial Al on hybrid InAs heterostructures with a conducting quantum well show similarly enhanced superconducting properties transferred to the two-dimensional electron gas (2DEG) by proximity effect, with critical perpendicular magnetic fields up to 3.5 T. An insulating AlOx film that passivates the heterostructure from exposure to air is obtained by complete oxidation of the Al. It simultaneously removes the need to strip Al which damages the underlying semiconductor. AO passivation yielded 2DEG mobilities two times higher than similar devices with Al removed by wet etching. An AO-passivated Hall bar showed quantum Hall features emerging at a transverse field of 2.5 T, below the critical transverse field of thinned films, eventually allowing transparent coupling of quantum Hall effect and superconductivity. AO thinning and passivation are compatible with standard lithographic techniques, giving lateral resolution below <50 nm. We demonstrate local patterning of AO by realizing a semiconductor-based Josephson junction operating up to 0.3 T perpendicular.

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  • Received 17 September 2020
  • Revised 28 November 2020
  • Accepted 7 December 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.5.013805

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Asbjørn C. C. Drachmann1,*, Rosa E. Diaz2, Candice Thomas2,3, Henri J. Suominen1, Alexander M. Whiticar1, Antonio Fornieri1, Sergei Gronin2,3,4, Tiantian Wang2,3, Geoffrey C. Gardner2,3,4,5, Alex R. Hamilton1,6,7, Fabrizio Nichele1,8, Michael J. Manfra2,3,4,5,9, and Charles M. Marcus1,†

  • 1Center for Quantum Devices and Microsoft Quantum Lab Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
  • 2Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
  • 3Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
  • 4Microsoft Quantum Purdue, Purdue University, West Lafayette, Indiana 47907, USA
  • 5School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
  • 6School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
  • 7Australian Research Centre of Excellence in Future Low Energy Electronics Technologies, University of New South Wales, Sydney, New South Wales 2052, Australia
  • 8IBM ResearchZurich, Sumerstrasse 4, 8803 Rschlikon, Switzerland
  • 9School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA

  • *asbjorn.drachmann@nbi.ku.dk
  • chmarcus@microsoft.com

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Issue

Vol. 5, Iss. 1 — January 2021

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