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

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 $\hat{I}½=2$ 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$\cdot$Ã 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 $\hat{I}¼$V and critical current densities up to 9.6 $\hat{I}¼$A/$\hat{I}¼$m, among the largest values reported for Nb-InAs SNS devices.

main text 8 pages with 3 figures; supplementary material 17 pages with 11 figures