Superconductor Science and Technology

Enhancement of the superconducting critical temperature of NbN ultra-thin films in a CMOS-compatible silicon nitride photonic platform on 200 mm-diameter wafers

Valentin Brisson, Edith Bellet-Amalric, Nicolas Bernier, Jonathan Faugier-Tovar, Matthew Bryan, Joël Bleuse, Jean‐Michel Gérard, S. Olivier

Published Mar 12, 2025• 2 citations

Publisher

Abstract

Abstract In this paper, we investigate the superconducting critical temperature, morphology and structural properties of NbN ultra-thin films (5–7 nm) deposited by reactive sputtering on top of silicon nitride (SiN) over 200 mm silicon wafers. We demonstrate the effectiveness of a 10 nm thick spacer layer of AlN in raising the superconducting critical temperature from 5.0 K to 7.2 K and from 7.3 K to 9.3 K for 5 nm and 7 nm NbN thickness respectively. By combining investigations with x-ray diffraction and transmission electron microscopy, we highlight significant modifications of the crystalline properties of the NbN film on top of the AlN spacer layer. When directly deposited on SiN, the grains of the NbN polycrystalline layer are randomly oriented. In contrast, when deposited on top of the AlN (0001) spacer layer, the NbN layer is textured along the (111) direction, leading to increased critical temperatures. As AlN is a CMOS-compatible material, these findings are particularly relevant in view of the future integration of high-performance superconducting nanowire single photon detectors on large-scale quantum photonic chips.

DOI: 10.1088/1361-6668/adbfc9

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