Highly Transparent Gatable Superconducting Shadow Junctions

Sabbir A. Khan, Charalampos Lampadaris, Ajuan Cui, Lukas Stampfer, Yu Liu, Sebastian J. Pauka, Martin E. Cachaza, Elisabetta M. Fiordaliso, Svetlana Korneychuk

Research output: Contribution to journalArticleScientificpeer-review

17 Citations (Scopus)


Gate-tunable junctions are key elements in quantum devices based on hybrid semiconductor-superconductor materials. They serve multiple purposes ranging from tunnel spectroscopy probes to voltage-controlled qubit operations in gatemon and topological qubits. Common to all is that junction transparency plays a critical role. In this study, we grow single-crystalline InAs, InSb, and InAs1-xSbx semiconductor nanowires with epitaxial Al, Sn, and Pb superconductors and in situ shadowed junctions in a single-step molecular beam epitaxy process. We investigate correlations between fabrication parameters, junction morphologies, and electronic transport properties of the junctions and show that the examined in situ shadowed junctions are of significantly higher quality than the etched junctions. By varying the edge sharpness of the shadow junctions, we show that the sharpest edges yield the highest junction transparency for all three examined semiconductors. Further, critical supercurrent measurements reveal an extraordinarily high ICRN, close to the KO-2 limit. This study demonstrates a promising engineering path toward reliable gate-tunable superconducting qubits.

Original languageEnglish
Pages (from-to)14605-14615
Number of pages11
JournalACS Nano
Issue number11
Publication statusPublished - 24 Nov 2020


  • ballistic transport
  • Majorana bound states
  • quantum computing
  • semiconductor−superconductor nanowires
  • shadow junctions
  • topological materials


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