Increasing the valley splitting in Si/SiGe heterostructures by exploiting atomic concentration fluctuations

ORAL

Abstract

We present a theory of how alloy disorder affects the intervalley coupling and valley splitting in quantum dot qubits in Si/SiGe heterostructures. We show that this theory is in good agreement with experiments as well as the NEMO-3D 20-band strain-dependent sp3d5s* tight-binding model. We find that, for realistic devices, alloy disorder is the dominant source of variation in the valley splitting.  Moreover, we show that increasing the alloy disorder increases the spread of the intervalley coupling, thereby increasing the average valley splitting. These results lead to a new and counterintuitive strategy for engineering quantum wells with large average valley splittings: increasing the alloy disorder. We find that adding just 5% Ge to the bottom of the quantum well enhances valley splittings substantially, achieving splittings larger than 100 μeV over 95% of the time. This strategy runs counter to the prevailing strategy of making devices with little disorder and very sharp interfaces.  

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Publication: ​​​​​​​Manuscript in progress. Brian Paquelet Wuetz, Merritt P. Losert, Sebastian Koelling, Lucas E.A. Stehouwer, Anne-Marije J. Zwerver, Stephan G.J. Philips, Mateusz T. Mądzik, Xiao Xue, Guoji Zheng, Mario Lodari, Sergey Amitonov, Nodar Samkharadze, Amir Sammak, Lieven M.K. Vanderspyen, Rajib Rahman, Susan N. Coppersmith, Oussama Moutanabbir, Mark Friesen, and Giordano Scappucci. "Role of atomic fluctuations in lifting energy degeneracy at a Si/SiGe interface."

Presenters

  • Merritt P Losert

    • University of Wisconsin-Madison

Authors

  • Merritt P Losert

    • University of Wisconsin-Madison

  • Brian Paquelet Wuetz

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, TU Delft, P.O. Box 5046, 2600 GA Delft, The Netherlands
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Sebastian Koelling

    • Ecole Polytechnique de Montreal
    • Department of Engineering Physics, École Polytechnique de Montréal

  • Lucas Stehouwer

    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Anne-Marije J Zwerver

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Stephan G Philips

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Mateusz T Madzik

    • Delft University of Technology
    • University of New South Wales
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Xiao Xue

    • TU Delft
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology
    • Delft University of Technology

  • Guoji Zheng

    • Intel Corporation
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Mario Lodari

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, TU Delft, P.O. Box 5046, 2600 GA Delft, The Netherlands
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Sergey V Amitonov

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Nodar Samkharadze

    • Delft University of Technology
    • QuTech and Netherlands Organisation for Applied Scientific Research

  • Amir Sammak

    • TNO
    • Netherlands Organization for Applied Scientific Research (TNO)
    • QuTech and TNO, Stieltjesweg 1, 2628 CK Delft, The Netherlands
    • QuTech and Netherlands Organisation for Applied Scientific Research

  • Lieven Vandersypen

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology

  • Rajib Rahman

    • University of New South Wales
    • Silicon Quantum Computing Pty Ltd., Level 2, Newton Building, UNSW Sydney, Kensington, NSW 2052, Australia

  • Sue N Coppersmith

    • University of New South Wales

  • Oussama Moutanabbir

    • Ecole Polytechnique de Montreal
    • École Polytechnique de Montréal
    • Department of Engineering Physics, École Polytechnique de Montréal

  • Mark G Friesen

    • University of Wisconsin - Madison

  • Giordano Scappucci

    • Delft University of Technology
    • QuTech and Kavli Institute of Nanoscience, TU Delft, P.O. Box 5046, 2600 GA Delft, The Netherlands
    • QuTech and Kavli Institute of Nanoscience, Delft University of Technology