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

TL;DR

This paper reports the development of a hybrid platform combining Nb superconducting films with GaAs semiconductors using in-situ deposition techniques, achieving high critical fields and revealing interface characteristics.

Contribution

It introduces a novel in-situ deposition method for Nb-GaAs hybrids, comparing it with ex-situ methods and analyzing interface properties and superconducting parameters.

Findings

Nb films exhibit critical temperatures around 9 K.

Critical magnetic fields reach up to 1.4 T at 4.2 K.

An amorphous interlayer forms at the GaAs-Nb interface.

Abstract

We present Nb thin films deposited in-situ on GaAs by combining molecular beam epitaxy and magnetron sputtering within an ultra-high 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 $9 \textrm{K}$. and critical perpendicular magnetic fields of up to $B_{c2} = 1.4 \textrm{T}$ at $4.2 \textrm{K}$. 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.