Development of Nb-GaAs based superconductor-semiconductor hybrid platform by combining in situ dc magnetron sputtering and molecular beam epitaxy

We present Nb thin films deposited in situ on GaAs by combining molecular beam epitaxy and magnetron sputtering within an ultrahigh vacuum cluster. Nb films deposited at varying power, and a reference film from a commercial system, are compared. The results show clear variation between the in situ and ex situ deposition which we relate to differences in magnetron sputtering conditions and chamber geometry. The Nb films have critical temperatures of around 9K and critical perpendicular magnetic fields of up to Bc2=1.4T at 4.2K. From STEM images of the GaAs-Nb interface we find the formation of an amorphous interlayer between the GaAs and the Nb for both the ex situ and in situ deposited material.