High transparency induced superconductivity in field effect two-dimensional electron gases in undoped InAs/AlGaSb surface quantum wells

TL;DR

This study demonstrates high-quality 2DEGs in InAs quantum wells with quantized Hall effects, large Rashba spin-orbit coupling, and proximitized superconductivity with high interface transparency, advancing potential quantum device applications.

Contribution

It reports the realization of high-transparency superconducting contacts and strong spin-orbit coupling in InAs 2DEGs, with detailed transport and superconducting properties.

Findings

Quantized integer quantum Hall effect up to filling factor 2.

Large Rashba spin-orbit coefficients up to 124 meV·Å.

High interface transparency (78-99%) in Nb-based SNS junctions.

Abstract

We report on transport characteristics of field effect two-dimensional electron gases (2DEG) in 24 nm wide indium arsenide surface quantum wells. High quality single-subband magnetotransport with clear quantized integer quantum Hall plateaus are observed to filling factor $\nu=2$ in magnetic fields of up to B = 18 T, at electron densities up to 8$\times 10^{11}$ /cm$^2$. Peak mobility is 11,000 cm$^2$/Vs at 2$\times 10^{12}$ /cm$^2$. Large Rashba spin-orbit coefficients up to 124 meV$\cdot$\r{A} are obtained through weak anti-localization (WAL) measurements. Proximitized superconductivity is demonstrated in Nb-based superconductor-normal-superconductor (SNS) junctions, yielding 78$-$99% interface transparencies from superconducting contacts fabricated ex-situ (post-growth), using two commonly-used experimental techniques for measuring transparencies. These transparencies are on a par with those reported for epitaxially-grown superconductors. These SNS junctions show characteristic voltages $I_c R_{\text{N}}$ up to 870 $\mu$V and critical current densities up to 9.6 $\mu$A/$\mu$m, among the largest values reported for Nb-InAs SNS devices.