InAs-AlSb quantum well as superconducting weak link with high critical current density

Abstract
We have constructed a superconductor‐semiconductor weak link using an InAs‐AlSb quantum well as the channel between Nb electrodes. The structure draws on (a) the barrier‐free nature of the Nb‐InAs interfaces and (b) the combination of high electron concentrations and very high electron mobilities in the InAs wells, which yield a large superconducting coherence length (3700 Å) inside the channel. A large (lineal) critical supercurrent density of 32 mA/mm was obtained at 1.4 K, for a channel length of 0.6 μm. After temporary exposure to a magnetic field, the current‐voltage characteristic became hysteretic, with an increase in critical current density to 132 mA/mm. The latter value corresponds to an areal current density of 8.8×105 A/cm2.