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–x Sb x 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 I C R N, close to the KO-2 limit. This study demonstrates a promising engineering path toward reliable gate-tunable superconducting qubits.

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Contactless time-resolved optical pump–probe and external quantum efficiency measurements were performed in epitaxially grown free-standing wurtzite indium arsenide/indium aluminum arsenide (InAs-InAlAs) core–shell nanowires on Si (111) substrate from 77 to 293 K. The first independent investigation of Shockley–Read–Hall, radiative, and Auger recombination in InAs-based NWs is presented. Although the Shockley–Read–Hall recombination coefficient was found to be at least 2 orders of magnitude larger than the average experimental values of other reported InAs materials, the Auger recombination coefficient was reported to be 10-fold smaller. The very low Auger and high radiative rates result in an estimated peak internal quantum efficiency of the core–shell nanowires as high as 22% at 77 K, making these nanowires of potential interest for high-efficiency mid-infrared emitters. A greater than 2-fold enhancement in minority carrier lifetime was observed from capping nanowires with a thin InAlAs shell due to the passivation of surface defects.

Understanding the spatial distribution of charge carriers in III–V nanowires proximity coupled to superconductors is important for the design and interpretation of experiments based on hybrid quantum devices. In this letter, the gate‐dependent surface accumulation layer of half‐shell InAsSb/Al nanowires is studied by means of Andreev interference in a parallel magnetic field. Both uniform hybrid nanowires and devices featuring a short Josephson junction fabricated by shadow lithography, exhibit periodic modulation of the switching current. The period corresponds to a flux quantum through the nanowire diameter and is consistent with Andreev bound states occupying a cylindrical surface accumulation layer. The spatial distribution is tunable by a gate potential as expected from electrostatic models.

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