Scattering Mechanisms of Near Surface Two Dimensional Electron Gas in Epitaxial InAs-Al Structures*

Increasing interest in superconducting proximity effect in semiconductors is driven by the recent proposal to realize hybrid topological materials for quantum information. The quality of the superconductor-semiconductor interface is crucial for these applications since the interface controls how the superconducting properties are imparted on the semiconductor. In this study, we grow epitaxial Al on InAs surface quantum well [1] using molecular beam epitaxy followed by structural and electrical characterization. In Hall bar geometry, the low temperature magnetotransport data exhibits high visibility of Shubnikov de-Haas oscillations and electron mobility near 40,000 cm²/Vs. Further transport studies are done with gated Hall bars and superconductor-semiconductor-superconductor (SNS) junctions. We analyze transport scattering mechanisms present in our heterostructures in detail and show the limiting factor in the mobility of our surface quantum wells are surface and ionized scattering. SNS junctions based on these structures exhibit high transparency and large supercurrent with product of critical current and normal resistance reaching the superconducting gap. [1] J. Shabani et al. PRB 2016