Shadow epitaxy for in-situ growth of generic semiconductor/superconductor devices

TL;DR

This paper introduces a novel crystal growth platform that enables in-situ synthesis of semiconductor/superconductor hybrids with patterned shells, eliminating etching and broadening material choices for high-performance nanoscale devices.

Contribution

The authors develop a shadow epitaxy method for in-situ growth of semiconductor/superconductor devices, allowing arbitrary material combinations and improved device quality.

Findings

Increased yield and electrostatic stability in hybrid devices.

Successful fabrication of devices with aluminium, tantalum, niobium, and vanadium.

Evidence of ballistic superconductivity in the new hybrids.

Abstract

Uniform, defect-free crystal interfaces and surfaces are crucial ingredients for realizing high-performance nanoscale devices. A pertinent example is that advances in gate-tunable and topological superconductivity using semiconductor/superconductor electronic devices are currently built on the hard proximity-induced superconducting gap obtained from epitaxial indium arsenide/aluminium heterostructures. Fabrication of devices requires selective etch processes; these exist only for InAs/Al hybrids, precluding the use of other, potentially superior material combinations. We present a crystal growth platform -- based on three-dimensional structuring of growth substrates -- which enables synthesis of semiconductor nanowire hybrids with in-situ patterned superconductor shells. This platform eliminates the need for etching, thereby enabling full freedom in choice of hybrid constituents. 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. This is the submitted version of the manuscript. The accepted, peer reviewed version is available from Advanced Materials: http://doi.org/10.1002/adma.201908411 Previous title: Shadow lithography for in-situ growth of generic semiconductor/superconductor devices