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

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.