Superconductor connection to InAs two-dimensional electrons with accumulation edges

Abstract

Natural two-dimensional electron gas (2DEG) on the surface of n-type InAs has been used for studying superconductor-semiconductor junctions. For high mobility and easiness in sample design, however, 2DEGs in quantum wells are more favorable. Even at the edges of such thin InAs films for quantum wells, one-dimensional (1D) electrons may be formed and give rise to various phenomena in transport. Such conduction through the 1D edge states is of interest in itself, but on the other hand, may give some artifacts in the study of superconductor-semiconductor junctions. Hence it is important to separate the 1D conduction through the accumulation edges. Here we report such edge states carry supercurrent and affect quantum Hall effect. The experiment was carried out in a strip of InAs two-dimensional electron gas with a quantum point contact (QPC) on one of the edges. Supercurrent was observed in low magnetic field, and the critical current decreased when the conductivity of QPC was reduced. In high magnetic field, the resistance showed dip structures in the transition region between quantum Hall plateaus. We infer that these characteristic transport properties come from negative band bending of InAs, which leads to charge accumulation on edges.