Inhomogeneous critical current in nanowire superconducting single-photon detectors

TL;DR

This study investigates the nanoscale uniformity of NbN superconducting films used in single-photon detectors, revealing significant inhomogeneity that impacts device performance.

Contribution

The paper introduces a method using short nanowire detectors to directly probe the nanoscale uniformity of NbN films, highlighting inhomogeneity issues.

Findings

NbN films are strongly inhomogeneous at the sub-100nm scale

Short nanowire detectors can effectively probe film uniformity

Inhomogeneity affects the performance and yield of SSPDs

Abstract

A superconducting thin film with uniform properties is the key to realize nanowire superconducting single-photon detectors (SSPDs) with high performance and high yield. To investigate the uniformity of NbN films, we introduce and characterize simple detectors consisting of short nanowires with length ranging from 100nm to 15{\mu}m. Our nanowires, contrary to meander SSPDs, allow probing the homogeneity of NbN at the nanoscale. Experimental results, endorsed by a microscopic model, show the strongly inhomogeneous nature of NbN films on the sub-100nm scale.