Two dimensional epitaxial InAs-Al superconducting systems
It has been recently realized that materials with strong spin orbit coupling can lead to novel states of matter such as topological insulators and superconductors. This exciting development might lead to a number of useful applications ranging from spintronics to quantum computing. Here, we present epitaxial growth of near surface InAs heterostructures where the structures are designed such that the charge distribution is mainly confined in InAs but has a non-zero value at the surface. This band engineering allows us to make ohmic contact to the 2DES while keeping the electron mobilities well above traditional surface structures. In addition, the Rashba parameter measured from weak antilocalization analysis exhibit a very large spin-orbit coupling due to highly asymmetric potentials near surface. We also show that near perfect interface and a highly transparent contact can be achieved using epitaxial growth of aluminum on near-surface InAs 2DESs. Indeed, superconductor-semiconductor-superconductor junctions fabricated on these wafers exhibit a supercurrent with superior properties compared to ex-situ deposition of superconducting metals. The supercurrent flowing through the semiconductor can be controlled by a gate voltage making a transistor where the current can be turned “off” and “on”. Our results show that these new systems could provide new possibilities to study new quantum transport phenomena in addition to topological superconductivity.