Single-Photon Detection, Kinetic Inductance, and Non-Equilibrium Dynamics in Niobium and Niobium Nitride Superconducting Nanowires

Anthony J. Annunziata, Daniel F. Santavicca, Joel Chudow +5 more

Anthony J. Annunziata, Daniel F. Santavicca, Luigi Frunzio +4 more

We characterize inductors fabricated from ultra-thin, approximately 100 nm wide strips of niobium (Nb) and niobium nitride (NbN). These nanowires have a large kinetic inductance in the superconducting state. The kinetic inductance scales linearly with the nanowire length, with a typical value of 1 nH µm(-1) for NbN and 44 pH µm(-1) for Nb at a temperature of 2.5 K. We measure the temperature and current dependence of the kinetic inductance and compare our results to theoretical predictions. We also simulate the self-resonant frequencies of these nanowires in a compact meander geometry. These nanowire inductive elements have applications in a variety of microwave frequency superconducting circuits.

Anthony J. Annunziata, A. Frydman, Michael J. Rooks +1 more

Anthony J. Annunziata, A. Frydman, Matthew O. Reese +3 more

We have fabricated and tested single photon detectors based on a current biased superconducting niobium nanowire patterned into a meander. The detectors are fabricated from high quality, ultra high vacuum sputtered niobium thin films on a sapphire substrate. For detection of single optical photons, we show that the superconductor's intrinsic kinetic inductance does not limit the reset time of the detector, which is ≈ 2 nanoseconds, in contrast to the longer reset times seen in niobium nitride detectors of similar size and geometry. We also describe a readout scheme for photon counting that is unique to Nb due to its lower resistivity. These detectors have applications in imaging of infrared photoemission from CMOS logic circuits as well as in optical communications and quantum information processing.

Tao Jia, Lin Kang, Labao Zhang +5 more

Shangjr Gwo, Chang-Wei Cheng, Yan-Jyun Liao +4 more

Abstract Superconducting nanowire single-photon detectors (SNSPDs) have become increasingly important for both classical and quantum applications requiring single-photon sensing. Most current SNSPDs based on superconducting niobium nitride (NbN) ultrathin films are fabricated utilizing polycrystalline or amorphous superconductor films, and film inhomogeneity and defectivity can cause significant issues. Here, we present an all-epitaxial approach for fabricating SNSPDs with integrated metal reflectors, semiconductor (dielectric) resonators, and superconductor nanowire detectors. A working example is realized by molecular-beam epitaxy growth of a tri-layered heterostructure, consisting of a titanium nitride (TiN) reflector with ~ 92% reflectivity at the telecommunication wavelength (1550 nm), an aluminum nitride (AlN) resonator with a broad optical transparency window, and a NbN nanowire on c -plane sapphire wafer. The all-epitaxial approach provides a manufacturable platform with superior material properties, as well as uniformity across the wafer, which manifest themselves in tunable material parameters of the superconducting nanowire, including normal-state resistance, superconducting critical temperature, superconducting critical current, and kinetic inductance. The optimized material properties can be utilized to achieve excellent SNSPD performance, including wafer-scale uniformity in device characteristics and broadband (~300 nm) system detection efficiency (>90%) centered at 1550 nm, suitable for large-scale detector arrays and wavelength-division multiplexing (WDM) applications.