Anodization-free fabrication process for high-quality cross-type Josephson tunnel junctions based on a Nb/Al-AlO${}_x$/Nb trilayer

Abstract

Josephson tunnel junctions form the basis for various superconducting electronic devices. For this reason, enormous efforts are routinely taken to establish and later on maintain a scalable and reproducible wafer-scale manufacturing process for high-quality Josephson junctions. Here, we present an anodization-free fabrication process for Nb/Al-AlO${}_x$/Nb cross-type Josephson junctions that requires only a small number of process steps and that is intrinsically compatible with wafer-scale fabrication. We show that the fabricated junctions are of very high-quality and, compared to other junction types, exhibit not only a significantly reduced capacitance but also an almost rectangular critical current density profile. Our process hence enables the usage of low capacitance Josephson junctions for superconducting electronic devices such as ultra-low noise dc-SQUIDs, microwave SQUID multiplexers based on non-hysteretic rf-SQUIDs and RFSQ circuits.

References in corpus (7)

• Properties of Unshunted and Resistively Shunted Nb/AlOx-Al/Nb Josephson Junctions With Critical Current Densities from 0.1 mA/μm^2 to 1 mA/μm^2
• High resolution measurements of the switching current in a Josephson tunnel junction: Thermal activation and macroscopic quantum tunneling
• Single-charge devices with ultrasmall Nb/AlOx/Nb trilayer Josephson junctions
• Planarized Fabrication Process With Two Layers of SIS Josephson Junctions and Integration of SIS and SFS π-Junctions
• Circuit with small-capacitance high-quality Nb Josephson junctions
• A 490 GHz planar circuit balanced Nb-Al${}_2$O${}_3$-Nb quasiparticle mixer for radio astronomy: Application to quantitative local oscillator noise determination
• Aluminum Hard Mask Technique for the Fabrication of High-Quality Submicron Nb/Al-AlOx/Nb Josephson Junctions