Sidewall spacer passivated epitaxial NbN/AlN/NbN Josephson junctions for superconducting qubit applications
Abstract
Epitaxial NbN/AlN/NbN Josephson junctions are promising alternatives to conventional Al/AlOx/Al junctions for superconducting qubits due to their crystalline tunnel barriers and the high transition temperature of NbN. However, their integration into quantum circuits typically requires complex fabrication processes involving amorphous interlayer dielectrics, which can degrade qubit coherence times. To address these issues, we developed sidewall spacer passivated epitaxial NbN/AlN/NbN junctions using a fabrication process that reduces both the volume of amorphous dielectric material and fabrication complexity. The fabricated junctions exhibited a large gap voltage of approximately 5.6 mV and low subgap leakage currents. By varying the thickness of the AlN tunnel barrier, high-quality junctions were fabricated over a wide range of critical current densities it Jc, from 0.3 to 104 A/cm2. In addition, the comparison of the current-voltage characteristics before and after buffered hydrofluoric acid treatment indicated that the wet etching process did not degrade the electrical characteristics of the junctions. These results establish a scalable fabrication process for epitaxial Josephson junctions and provide a promising platform for high-coherence nitride-based superconducting qubits.
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BibTeX
@misc{honda2026sidewall,
title = {{Sidewall spacer passivated epitaxial NbN/AlN/NbN Josephson junctions for superconducting qubit applications}},
author = {Koki Honda and Daiki Kurihara and Hiroki Kutsuma and Hirotaka Terai and Taro Yamashita},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04820},
eprint = {2610.04820},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04820},
}
RIS
TY - UNPB
TI - Sidewall spacer passivated epitaxial NbN/AlN/NbN Josephson junctions for superconducting qubit applications
AU - Koki Honda
AU - Daiki Kurihara
AU - Hiroki Kutsuma
AU - Hirotaka Terai
AU - Taro Yamashita
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.04820
UR - https://arxiv.org/abs/2610.04820
AB - Epitaxial NbN/AlN/NbN Josephson junctions are promising alternatives to conventional Al/AlO_x/Al junctions for superconducting qubits due to their crystalline tunnel barriers and the high transition temperature of NbN. However, their integration into quantum circuits typically requires complex fabrication processes involving amorphous interlayer dielectrics, which can degrade qubit coherence times. To address these issues, we developed sidewall spacer passivated epitaxial NbN/AlN/NbN junctions using a fabrication process that reduces both the volume of amorphous dielectric material and fabrication complexity. The fabricated junctions exhibited a large gap voltage of approximately 5.6 mV and low subgap leakage currents. By varying the thickness of the AlN tunnel barrier, high-quality junctions were fabricated over a wide range of critical current densities it J_c, from 0.3 to 10^4 A/cm^2. In addition, the comparison of the current-voltage characteristics before and after buffered hydrofluoric acid treatment indicated that the wet etching process did not degrade the electrical characteristics of the junctions. These results establish a scalable fabrication process for epitaxial Josephson junctions and provide a promising platform for high-coherence nitride-based superconducting qubits.
ER -