N-InAs/GaAs heterostructure superconducting weak links with Nb electrodes

We report on the fabrication and characterization of planar superconductor-normal-superconductor (SNS) weak links in which the normal region is deposited n-InAs. The InAs is part of a heterostructure consisting of 100 nm of n-InAs grown on an undoped GaAs buffer layer on a semi-insulating GaAs substrate. The superconductor is Nb, patterned by electron beam lithography with interelectrode spacings as small as 260 nm. Device behavior is well explained by SNS weak link theory, with coherence lengths calculated from measured material parameters. These heterostructure weak links can be the basis for superconducting field-effect devices. They have the significant advantage of allowing simple device isolation compared with bulk InAs, which has been used in previous attempts to make such devices.