Enhanced Athermal Phonon Responsivity in a Kinetic Inductance Detector with Integrated Phonon Collectors

TL;DR

This work introduces an improved KID design with integrated phonon collectors, significantly boosting phonon collection efficiency for cryogenic particle detection applications.

Contribution

The paper presents a novel detector architecture where phonon collectors enhance responsivity by funneling athermal phonons to the sensor, achieving a sevenfold increase in collection efficiency.

Findings

Phonon collection efficiency increased by a factor of around 7.

The new design separates the KID sensor from phonon collectors for improved performance.

The detector uses a trilayer aluminum-titanium-aluminum meander and aluminum collectors.

Abstract

Cryogenic phonon detectors are adopted in light dark matter searches and coherent elastic neutrino-nucleus scattering experiments as they can achieve low energy thresholds. The phonon mediated sensing of silicon particle absorbers has already been proved with Kinetic Inductance Detectors (KIDs), acting both as sensors and athermal phonon absorbers. In this work we present the design and the performance of an improved detector design. In this architecture, the KID acts only as sensor and is coupled to dedicated phonon collectors. When a signal is coming from the substrate, the presence of a separated collector allows to detect an higher increase of quasi-particles density, thereby enhancing its responsivity. The meander of the KID is composed of a 77 nm trilayer wire of Aluminum-Titanium-Aluminum, while the phonon collectors are made of a 100 nm Aluminum layer and act as quasi-particles funnels. Inside the collectors, the absorbed athermal phonons generate quasi-particles which, after diffusion, are trapped in the lower-gap superconducting trilayer. The performance of this setup is compared to that of a standard phonon-mediated KID, showing an increased phonon collection efficiency by a factor of around 7.