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arXiv · 2206.00569

Hard superconducting gap in germanium

Alberto Tosato·Vukan Levajac·Ji-Yin Wang·Casper J. Boor·Francesco Borsoi·Marc Botifoll·Carla N. Borja·Sara Martí-Sánchez·Jordi Arbiol·Amir Sammak·Menno Veldhorst·Giordano Scappucci
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Abstract

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 because obtaining a superconducting gap free of subgap states (hard gap) has proven difficult. Here we solve 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 (Pt) and the semiconductor heterostructure (Ge/SiGe). 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.

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Alberto Tosato, Vukan Levajac, Ji-Yin Wang, Casper J. Boor, Francesco Borsoi, Marc Botifoll, Carla N. Borja, Sara Martí-Sánchez, Jordi Arbiol, Amir Sammak, Menno Veldhorst, Giordano Scappucci. 2022-06-01. Hard superconducting gap in germanium. https://doi.org/10.1038/s43246-023-00351-w

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