Enhanced Superconducting Nanowire Single Photon Detector Performances using Silicon Capping

TL;DR

This study demonstrates that silicon capping layers improve NbTiN superconducting nanowire detectors by preventing oxidation, enabling thinner films, wider wires, and extending detection capabilities into the near-infrared spectrum.

Contribution

The paper introduces the use of silicon capping layers to enhance NbTiN SNSPDs, addressing fabrication challenges and performance degradation issues.

Findings

Silicon capping suppresses oxidation and raises superconducting transition temperature.

Thinner films (as thin as 3 nm) can achieve superconductivity at 3 K.

Extended detection wavelength up to 2050 nm with maintained sub-50 ps jitter.

Abstract

Niobium Titanium nitride (NbTiN) based superconducting nanowire single photon detectors (SNSPDs) are known for their high performance across a wide spectral range, from the X-ray to the mid-infrared. Nonetheless, fabrication challenges and performance degradation attributable to surface oxidation and lack of uniformity in films thinner than 5 nm remain a significant barrier for achieving high-quality detectors. In this work, we study the influence of a Silicon capping layer on film properties and on the performance of SNSPDs. A Silicon capping layer effectively suppresses oxidation and increases the superconducting transition temperature. This enables superconductivity in films as thin as 3 nm at 3 K, increases critical current in patterned nanowires and significantly extends the saturation plateau from the visible to the near infrared (up to 2050 nm): These detectors maintain sub-50 ps timing jitter, even for nanowires as wide as 250 nm and with detection areas of 20x20{\mu}m2. Our results establish that thinner films protected by a capping layer allow for the fabrication of wider wires, decreasing nanofabrication challenges and extending the operating temperature range for efficient single photon detection.