Superconducting vanadium/indium-arsenide hybrid nanowires

Bjergfelt, Martin; Carrad, Damon J.; Kanne, Thomas; Aagesen, Martin; Fiordaliso, Elisabetta Maria; Johnson, Erik; Shojaei, Borzoyeh; Palmstrøm, C. J.; Krogstrup, Peter; Jespersen, Thomas Sand; Nygård, Jesper

doi:10.1088/1361-6528/ab15fc

Cited by 34 publications

(48 citation statements)

References 41 publications

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“…To ensure a pristine interface, the sample remains under ultrahigh vacuum (<10 −8 Torr) between NW growth and SU deposition. [ 8,10,11,24,31 ] In the simplest, single‐deposition case, the SU coats two or three of the NW's six facets—i.e., a half‐shell coating—except for regions shadowed by the bridge. This breaks the NW into a sequence of SU segments separated by bare SE.…”

Section: Figurementioning

confidence: 99%

“…Δ H vap Ta,Nb ≈ 700 kJ mol −1 . [ 8,31 ] Note that these effects can be compensated for by, e.g., altering mask design and NW position, using a smaller deposition source or collimator, and/or double‐angle evaporation (Section 2, Supporting Information).…”

Section: Figurementioning

confidence: 99%

“…Such double‐angle‐generated structures produce both lateral and axial hybrid devices made from a range of possible constituent materials—including normal metals, SUs and/or magnetic elements—with pristine epitaxial interfaces. Double‐angle deposition also enables JJ devices with arbitrarily short junction length, as demonstrated in Figure 5c for a vanadium‐based hybrid [ 31 ] made by two depositions from different angles θ 1 = 16 o , θ 2 = 17 o . Conveniently, the SE segment length l SE depends not only on the angles θ 1 and θ 2 , but also on the separation S between bridge and NW.…”

Section: Figurementioning

confidence: 99%

“…The shadow epitaxy platform enables independent materials choice (SU, SE) and we demonstrate simultaneous growth of the most important hybrid device architectures using aluminum, niobium, tantalum, and vanadium. [ 31 ] Eliminating post‐process chemical etching increased spectroscopic device yield (5 out of 5 for Al and Ta devices), enabled ballistic superconductivity in Nb devices, and enhanced electrostatic stability by an order of magnitude in Majorana island devices. Very high yield and large‐range, hysteresis‐free device operation are crucial metrics for future advanced circuitry that incorporates a large number of hybrid elements.…”

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confidence: 99%

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Shadow Epitaxy for In Situ Growth of Generic Semiconductor/Superconductor Hybrids

et al. 2020

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The quality of interfaces and surfaces is crucial for the performance of nanoscale devices. A pertinent example is the close tie between current progress in gate-tunable and topological superconductivity using semiconductor/superconductor electronic devices and the hard proximity-induced superconducting gap obtained from epitaxial indium arsenide/aluminium heterostructures. Fabrication of devices requires selective etch processes; these only exist for InAs/Al hybrids, which precludes the use of other, potentially better material combinations in functional devices. We present a crystal growth platform based on three-dimensional structuring of growth substrates for synthesising semiconductor nanowires with in-situ patterned superconductor shells, which enables independent choice of material by eliminating etching. We realise and characterise all the most frequently used architectures in superconducting hybrid devices, finding increased yield and electrostatic stability compared to etched devices, along with evidence of ballistic superconductivity. In addition to aluminium, we present hybrid devices based on tantalum, niobium and vanadium.One dimensional semiconductor (SE) nanowires (NWs) proximity coupled to superconductors (SU) have attracted considerable attention from the condensed matter community since the prediction 1,2 and observation of Majorana zero-modes 3-5 , which have been proposed as a basis for topologically protected quantum information processors 6,7 . To ensure topological protection, methods for growing disorder-free 'hard-gap' SE/SU epitaxial hybrids were developed 8-10 . These materials utilise bottom-up crystal growth of InAs nanowires with uniform epitaxial aluminium coatings, an approach which has been extended to high mobility two-dimensional systems 11,12 and selective area grown networks 13,14 . The success of epitaxial InAs/Al hybrids lies in the ability to realise important device classes such as normal metal spectroscopic devices, 5,9,11,12 Josephson Junctions 15-18 for gate-controlled transmon qubits 19,20 , and superconducting Majorana islands 21-23 , using top-down processing to selectively remove the Al. A limitation of this method is that relying on post-process etching inherently limits materials choice. For instance, despite strong incentives to utilise technologically important superconductors such as Nb 24 and NbTiN 25 -which exhibit higher transition temperatures, critical magnetic fields and superconducting energy gaps -selectively removing Nb from InAs remains an unsolved problem. Similarly, InSb is an attractive semiconductor due to its high mobility, g-factor and strong spin-orbit coupling 25-28 . Yet, selectively removing even aluminum from InSb without damage is impossible with known methods. Thus, most potential improvements in epitaxial SE/SU technology are predicated on developing a materials-independent method for device fabrication. An attractive approach to eliminate etching is to employ an in-situ 'shadow approach' to mask specific segments along the NW from supe...

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

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Shadow Epitaxy for In Situ Growth of Generic Semiconductor/Superconductor Hybrids

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“…Thus, for example, aluminium with a small superconducting gap and a small critical magnetic eld but large superconducting coherence length is a common choice. 1,13,16 For higher temperatures or higher magnetic elds operation, superconductors such as Nb and its alloys, 3,15,17,18 Pb, 19,20 or V, 21,22 are used. However, detailed analysis of these semiconductor/superconductor systems are just starting to emerge.…”

Section: Introductionmentioning

confidence: 99%

Fully in situ Nb/InAs-nanowire Josephson junctions by selective-area growth and shadow evaporation

et al. 2021

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Single‐Shot Fabrication of Semiconducting–Superconducting Nanowire Devices

Borsoi

Mazur

Loo

et al. 2021

Adv Funct Materials

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Semiconducting–superconducting hybrids are vital components for the realization of high‐performance nanoscale devices. In particular, semiconducting–superconducting nanowires attract widespread interest owing to the possible presence of non‐abelian Majorana zero modes, which are quasiparticles that hold promise for topological quantum computing. However, systematic search for Majoranas signatures is challenging because it requires reproducible hybrid devices and reliable fabrication methods. This work introduces a fabrication concept based on shadow walls that enables the in situ, selective, and consecutive depositions of superconductors and normal metals to form normal‐superconducting junctions. Crucially, this method allows to realize devices in a single shot, eliminating fabrication steps after the synthesis of the fragile semiconductor/superconductor interface. At the atomic level, all investigated devices reveal a sharp and defect‐free semiconducting–superconducting interface and, correspondingly, a hard induced superconducting gap resilient up to 2 T is measured electrically. While the cleanliness of the technique enables systematic studies of topological superconductivity in nanowires, it also allows for the synthesis of advanced nano‐devices based on a wide range of material combinations and geometries while maintaining an exceptionally high interface quality.

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Superconducting vanadium/indium-arsenide hybrid nanowires

Cited by 34 publications

References 41 publications

Shadow Epitaxy for In Situ Growth of Generic Semiconductor/Superconductor Hybrids

Shadow Epitaxy for In Situ Growth of Generic Semiconductor/Superconductor Hybrids

Fully in situ Nb/InAs-nanowire Josephson junctions by selective-area growth and shadow evaporation

Single‐Shot Fabrication of Semiconducting–Superconducting Nanowire Devices

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