Maximizing absorption in photon trapping ultra-fast silicon photodetectors

TL;DR

This paper explores optimizing photon trapping structures in silicon photodetectors to significantly boost broadband absorption and speed, enabling more efficient high-speed near-infrared detection for applications like LIDAR and quantum communication.

Contribution

It introduces design strategies and empirical models for photon trapping structures that enhance absorption and reduce capacitance in high-speed silicon photodetectors.

Findings

Broadband absorption efficiency increased by up to 1000%.

Capacitance reduced by more than 50%.

Empirical equations relate quantum efficiency to physical and fabrication parameters.

Abstract

Silicon photodetectors operating at near-infrared wavelengths with high-speed and high sensitivity are becoming critical for emerging applications, such as Light Detection and Ranging Systems (LIDAR), quantum communications, and medical imaging. However, such photodetectors present a bandwidth-absorption trade-off at those wavelengths that have limited their implementation. Photon trapping structures address this trade-off by enhancing the light-matter interactions, but maximizing their performance remains a challenge due to a multitude of factors influencing their design and fabrication. In this paper, strategies to improve the photon trapping effect while enhancing the speed of operation are investigated. By optimizing the design of photon trapping structures and experimentally integrated them in high-speed photodetectors, a simultaneous broadband absorption efficiency enhancement up to 1000% and a capacitance reduction of more than 50% has been achieved. Such work also allows to present empirical equations to correlate the quantum efficiency of photodetectors with the physical properties of the photon-trapping structures, material characteristics, and limitations of the fabrication technologies. The results obtained, open routes towards designing cost-effective CMOS integrated.