Toward durable Al-InSb hybrid heterostructures via epitaxy of 2ML interfacial InAs screening layers

The large Landé $g$ factor, high spin-orbit coupling, and low effective mass of the two-dimensional electron gas in InSb quantum wells combined with proximal superconductivity may realize a scalable platform for topological quantum computation. Aluminum thin films directly deposited on top of InSb planar structures result in the formation of a reactive AlInSb layer at the interface. This interlayer progressively consumes the whole Al film, resulting in a disordered AlInSb layer after a few months at room temperature. We report on a heterostructure design that results in a significant increase of the durability of these hybrid Al-InSb heterostructures with the preservation of a pure Al film and sharp superconductor-semiconductor interface for more than one year. Two monolayers of epitaxial InAs at the superconductor-semiconductor interface prevent interfacial reactivity as evidenced by x-ray reflectivity and energy dispersive spectroscopy measurements. Structural characterizations of the Al films by transmission electron microscopy reveal the presence of tens of nanometers wide grains predominantly oriented with Al(110) parallel to InSb(001).