Hybrid superconductor/semiconductor step junctions with three terminals

We report on experimental results with three-terminal superconductor/semiconductor hybrid junctions, which are based on the two-dimensional electron gas at the surface of p-type InAs. A short distance (≈150 nm) between superconducting Nb contacts is obtained using a step geometry. The step geometry allows the realization of different heterostructure potential profiles along the two-dimensional channel. The critical current of the step junctions can be controlled by applying a voltage to highly doped (δ-doped) layers embedded in the heterostructure. With p-δ-doped layers, a p-n junction is introduced in the two-dimensional channel and an asymmetric change of the critical current with respect to the gate voltage or gate current is observed. With n-δ-doped layers, the change is symmetrical.