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

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 ν=2 in magnetic fields of up to B = 18 T, at electron densities up to 8× 10^11 /cm^2. Peak mobility is 11,000 cm^2/Vs at 2× 10^12 /cm^2. Large Rashba spin-orbit coefficients up to 124 meV·Å are obtained through weak anti-localization (WAL) measurements. Proximitized superconductivity is demonstrated in Nb-based superconductor-normal-superconductor (SNS) junctions, yielding 78-99 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_N up to 870 μV and critical current densities up to 9.6 μA/μm, among the largest values reported for Nb-InAs SNS devices.