Hole gases in planar germanium can have high mobilities in combination with strong spin-orbit interaction and electrically tunable g factors, and are therefore emerging as a promising platform for creating hybrid superconductor-semiconductor devices. A key challenge towards hybrid Ge-based quantum technologies is the design of high-quality interfaces and superconducting contacts that are robust against magnetic fields. In this work, by combining the assets of aluminum, which provides good contact to the Ge, and niobium, which has a significant superconducting gap, we demonstrate highly transparent low-disordered JoFETs with relatively large ICRN products that are capable of withstanding high magnetic fields. We furthermore demonstrate the ability of phase-biasing individual JoFETs, opening up an avenue to explore topological superconductivity in planar Ge. The persistence of superconductivity in the reported hybrid devices beyond 1.8 T paves the way towards integrating spin qubits and proximity-induced superconductivity on the same chip.
Physical Review Research
This research and related results were made possible with the support of the NOMIS Foundation. This research was supported by the Scientific Service Units of IST Austria through resources provided by the MIBA Machine Shop and the nanofabrication facility, the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant agreement No. 844511 Grant Agreement No. 862046. ICN2 acknowledge funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autnoma de Barcelona Materials Science PhD program. The HAADF-STEM microscopy was conducted in the Laboratorio de Microscopias Avanzadas at Instituto de Nanociencia de Aragon-Universidad de Zaragoza. Authors acknowledge the LMA-INA for offering access to their instruments and expertise. We acknowledge support from CSIC Research Platform on Quantum Technologies PTI-001. This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 823717 ESTEEM3. M.B. acknowledges support from SUR Generalitat de Catalunya and the EU Social Fund; project ref. 2020 FI 00103. G.S. and M.V. acknowledge support through a projectruimte grant associated with the Netherlands Organization of Scientific Research (NWO). J.D. acknowledges support through FRIPRO-project 274853, which is funded by the Research Council of Norway.
Aggarwal K, Hofmann AC, Jirovec D, et al. Enhancement of proximity-induced superconductivity in a planar Ge hole gas. Physical Review Research. 2021;3(2). doi:10.1103/physrevresearch.3.l022005
Aggarwal, K., Hofmann, A. C., Jirovec, D., Prieto Gonzalez, I., Sammak, A., Botifoll, M., … Katsaros, G. (2021). Enhancement of proximity-induced superconductivity in a planar Ge hole gas. Physical Review Research. American Physical Society. https://doi.org/10.1103/physrevresearch.3.l022005
Aggarwal, Kushagra, Andrea C Hofmann, Daniel Jirovec, Ivan Prieto Gonzalez, Amir Sammak, Marc Botifoll, Sara Martí-Sánchez, et al. “Enhancement of Proximity-Induced Superconductivity in a Planar Ge Hole Gas.” Physical Review Research. American Physical Society, 2021. https://doi.org/10.1103/physrevresearch.3.l022005.
K. Aggarwal et al., “Enhancement of proximity-induced superconductivity in a planar Ge hole gas,” Physical Review Research, vol. 3, no. 2. American Physical Society, 2021.
Aggarwal K, Hofmann AC, Jirovec D, Prieto Gonzalez I, Sammak A, Botifoll M, Martí-Sánchez S, Veldhorst M, Arbiol J, Scappucci G, Danon J, Katsaros G. 2021. Enhancement of proximity-induced superconductivity in a planar Ge hole gas. Physical Review Research. 3(2), L022005.
Aggarwal, Kushagra, et al. “Enhancement of Proximity-Induced Superconductivity in a Planar Ge Hole Gas.” Physical Review Research, vol. 3, no. 2, L022005, American Physical Society, 2021, doi:10.1103/physrevresearch.3.l022005.
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