Hard superconducting gap in germanium

Alberto Tosato, Vukan Levajac, Ji Yin Wang, Casper J. Boor, Francesco Borsoi, Marc Botifoll, Amir Sammak, Menno Veldhorst, Giordano Scappucci*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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The co-integration of spin, superconducting, and topological systems is emerging as an exciting pathway for scalable and high-fidelity quantum information technology. High-mobility planar germanium is a front-runner semiconductor for building quantum processors with spin-qubits, but progress with hybrid superconductor-semiconductor devices is hindered by the difficulty in obtaining a superconducting hard gap, that is, a gap free of subgap states. Here, we address this challenge by developing a low-disorder, oxide-free interface between high-mobility planar germanium and a germanosilicide parent superconductor. This superconducting contact is formed by the thermally-activated solid phase reaction between a metal, platinum, and the Ge/SiGe semiconductor heterostructure. Electrical characterization reveals near-unity transparency in Josephson junctions and, importantly, a hard induced superconducting gap in quantum point contacts. Furthermore, we demonstrate phase control of a Josephson junction and study transport in a gated two-dimensional superconductor-semiconductor array towards scalable architectures. These results expand the quantum technology toolbox in germanium and provide new avenues for exploring monolithic superconductor-semiconductor quantum circuits towards scalable quantum information processing.

Original languageEnglish
Article number23
Number of pages9
JournalCommunications Materials
Issue number1
Publication statusPublished - 2023


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