Epitaxial aluminium-nitride tunnel barriers grown by nitridation with a plasma source

TL;DR

This paper reports the successful growth of high-quality aluminium nitride tunnel barriers using plasma nitridation, achieving high current densities and improved reproducibility over traditional oxide barriers, with implications for superconducting junctions.

Contribution

It introduces a novel plasma nitridation method for growing uniform aluminium nitride barriers with high critical current densities and better reproducibility than previous techniques.

Findings

Achieved high critical current densities of 10 to 420 kA/cm^2.

Poly-crystalline AlN barriers are more uniform than AlO_x barriers.

Enhanced reproducibility and control in barrier fabrication.

Abstract

High critical current-density (10 to 420 kA/cm^2) superconductor-insulator-superconductor tunnel junctions with aluminium nitride barriers have been realized using a remote nitrogen plasma from an inductively coupled plasma source operated in a pressure range of 10^{-3} to 10^{-1} mbar. We find a much better reproducibility and control compared to previous work. From the current-voltage characteristics and cross-sectional TEM images it is inferred that, compared to the commonly used AlO_x barriers, the poly-crystalline AlN barriers are much more uniform in transmissivity, leading to a better quality at high critical current-densities.