Control over epitaxy and the role of the InAs/Al interface in hybrid two-dimensional electron gas systems

The interface quality in semiconductor/superconductor (SE/SC) platforms plays a crucial role for the superconducting coupling strength. In this work, a novel growth approach to grow grain-boundary-free Al on a lattice-mismatched InAs quantum well is introduced. More specifically, a monocrystalline Al phase is achieved by intentional roughening of the semiconductor surface. This approach can in general be applied to other mismatched material systems where a high degree of crystallinity is essential. Furthermore, the authors investigate the altered interfaces in transport measurements, hoping to shed more light upon the pressing question: ``What is the role of the detailed crystallography of the SC for the performance of SE/SC hybrid devices?''