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 ≈3,Ω,μm2. 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.
@article{arxiv.2512.06994,
title = {Fabrication and characterization of Nb/Al-AlN /Nb superconducting tunnel junctions},
author = {Alexey Pavolotsky and François Joint and Udupa Sujit Manjunatha and Victor Belitsky and Denis Meledin and Takafumi Kojima and Sho Masui and Ravishankar Narayanan and Vincent Desmaris},
journal= {arXiv preprint arXiv:2512.06994},
year = {2025}
}