Shadow Epitaxy for In Situ Growth of Generic Semiconductor/Superconductor Hybrids
Dr Thomas Sand Jespersen
Niels Bohr Institute / University of Copenhagen
Thomas Sand Jespersen is an experimental physicist working at the intersection between material science and mesoscopic low temperature electron quantum transport and mesoscopic devices. He received his PhD from the Niels Bohr Institute in 2007 and has worked as a visiting scholar at Harvard University and University of California, Berkeley. He is the author of 52 research articles and 6 patents and is currently associate professor at the Center for Quantum Devices, NBI, Denmark.
Recently epitaxial semiconductor/superconductor hybrid nanowires have received considerable attention partly due to possible applications in the field of topological quantum information processing. The main material system has been the InAs/Al hybrid nanowire which, in addition to the a hard induced gap, has the crucial possibility for easy and selective processing of the Al when designing devices and experiments. Other materials such as InSb semiconductors with higher mobilities and spin-orbit coupling, and e.g. Nb superconductors with higher Tc and Bc do not allow for selective processing and are therefore excluded from the traditional method of in situ epitaxial hybrid growth. Here, I will present a new growth platform -- shadow epitaxy -- for growing semiconductor/superconductor hybrids with in situ patterning performed in parallel on all nanowires simultaneously. The method obviates the need for selective post-processing, is generally compatible with any metal, and provides a considerable flexibility in device design. In addition to expanding the choices of materials we find that the stability and reproducible of in situ devices is significantly improved compared to traditional devices which is crucial for future complex hybrid device architectures.
 D. J. Carrad et al., Advances Materials, 32 1908411 (2020)