Superconducting Proximity Effect in InAsSb Surface Quantum Wells with in Situ Al Contacts

We demonstrate a robust superconducting proximity effect in InAs0.5Sb0.5 quantum wells grown with epitaxial Al contacts, which has important implications for mesoscopic and topological superconductivity. Unlike more commonly studied InAs and InSb semiconductors, bulk InAs0.5Sb0.5 supports stronger spin-orbit coupling and a larger g-factor. However, these potentially desirable properties have not been previously measured in epitaxial heterostructures with superconductors, which could serve as a platform for fault-tolerant topological quantum computing. Through structural and transport characterization, we observe high-quality interfaces and a strong spin-orbit coupling. We fabricate Josephson junctions based on InAs0.5Sb0.5 quantum wells and observe a strong proximity effect. With a contact separation of 500 nm, these junctions exhibit products IcRN = 270 μV and IexRN = 230 μV of normal resistance RN, critical current Ic, and excess current Iex. Both of these quantities demonstrate a robust and long-range proximity effect with highly transparent contacts.