Giant enhancement of silicon plasmonic SWIR photodetection using nanoscale self-organised metallic films

TL;DR

This paper presents a CMOS-compatible fractal aluminium nanostructure that significantly enhances silicon-based SWIR photodetectors' responsivity and sensitivity through plasmonic effects, enabling broad spectral detection and sensing.

Contribution

It introduces a novel fractal nanostructured aluminium film for hot carrier injection, achieving two orders of magnitude performance improvements in SWIR photodetection.

Findings

Two orders of magnitude increase in responsivity and detectivity.

Broad wavelength and angular range of enhanced absorption.

Structural parameters directly influence quantum efficiency.

Abstract

Many consumer technologies and scientific methods rely on photodetection of infrared light. We report a Schottky photodetector operating below silicon's band gap energy, through hot carrier injection from a nanoscale metallic absorber. Our design relies on simple CMOS-compatible 'bottom up' fabrication of fractally nanostructured aluminium films. Due to the fractal nature of the nanostructuring, the aluminium films support plasmonically enhanced absorption over a wide wavelength range. We demonstrate two orders of magnitude improvements of responsivity, noise-equivalent-power, and detectivity as compared to bulk metal, over a broad spectral and angular range. We attribute this to momentum relaxation processes from the nanoscale fractal geometry. Specifically, we demonstrate a direct link between quantum efficiency enhancement and structural parameters such as perimeter to surface ratio. Finally, our devices also function as bulk refractive index sensors. Our approach is a promising candidate for future cost effective and robust short wave infrared photodetection and sensing applications.