Epitaxial growth of superconducting NbN on wide-bandgap AlN

Abstract

NbN is a superconducting material used in single-photon detectors and quantum bits. Because NbN is lattice-matched to the wide-gap semiconductor AlN, it is possible to integrate the functions of nitride semiconductors and superconductors via epitaxial growth. However, the basic properties of NbN thin films epitaxially grown on nitride semiconductors are still unclear. In this study, we show the structural and electrical properties of NbN thin films grown on AlN by sputtering. We also discuss how the difference in the crystal structure between AlN and NbN leads to the formation of NbN twins.