InAs nanowire Josephson junctions with in-situ grown full shell Al

Superconductor-semiconductor hybrid nanowires are ideal material systems for studying various quantum transport phenomena such as Andreev and Majorana bound states. For quantum information technologies based on these quantum phenomena, it is highly desirable to develop hybrid nanowires with high-quality superconductor-semiconductor interfaces and ballistic transport in the semiconductor. In this study, we use shadow mask structures on the growth substrate to grow full shell Al-InAs-Al Josephson junction nanowires in situ. The in-situ grown junction can be free from surface damage and over-etching associated with the Al etching process. Electrical characterization of the Josephson junctions shows a hard superconducting gap. We observe multiple Andreev reflections in the open-channel regime and sub-gap states in the tunnel coupled regime. Furthermore, as a result of fluxoid quantization in the Al shell, the superconductivity is modulated by the magnetic flux and its effect on the Josephson junction is investigated.