Fabrication and characterization of Nb/Al-AlN/Nb superconducting tunnel junctions
Journal article, 2026
We report a Nb/Al-AlN/Nb superconducting tunnel junction process in which the AlN barrier is formed by plasma nitridation using a compact microwave electron cyclotron resonance (ECR) nitrogen plasma source integrated into a standard sputter cluster. This enables growth of uniform tunnel barriers across a broad range of specific resistances, with RnA down to similar or equal to 3 Omega mu m2. Junctions maintain excellent quality, exhibiting Rj/Rn >= 25 at the highest barrier transparencies. We characterize resistivity, specific capacitance, and the evolution of junction parameters under room temperature aging and thermal annealing. A consistent calibration of the junction specific capacitance Cs versus RnA is established and independently validated by the performance of demonstrator SIS mixers designed using the extracted Cs.
specific capacitance
Nb/Al-AlN/Nb SIS junctions
SIS junctions thermal stability
AlN tunnel barrier
superconducting circuits
millimeter/submillimeter mixers
Author
Alexei Pavolotski
Chalmers, Space, Earth and Environment, Onsala Space Observatory
François Joint
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Udupa Sujit Manjunatha
Indian Institute of Science
Victor Belitsky
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Denis Meledin
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Takafumi Kojima
Fujitsu Ltd
National Astronomical Observatory of Japan
Sho Masui
National Astronomical Observatory of Japan
Ravishankar Narayanan
Indian Institute of Science
Vincent Desmaris
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Superconductor Science and Technology
0953-2048 (ISSN) 1361-6668 (eISSN)
Vol. 39 1 015005Subject Categories (SSIF 2025)
Nano-technology
Physical Sciences
DOI
10.1088/1361-6668/ae2f33