# High bandwidth waveguide-integrated plasmonic germanium photodetector

## TL;DR

This paper introduces a waveguide-integrated plasmonic germanium photodetector with high responsivity and bandwidth, utilizing a dielectric-loaded surface plasmon polariton waveguide for efficient light-matter interaction and fast signal processing.

## Contribution

It presents a novel design of a plasmonic germanium photodetector with high responsivity and bandwidth, leveraging a long-range dielectric-loaded waveguide configuration for improved performance.

## Key findings

- Responsivity exceeds 1 A/W at 1310 nm and 1550 nm.
- Device length is 5 μm for 1310 nm and 30 μm for 1550 nm.
- Bandwidth exceeds 100 GHz, potentially over 150 GHz with optimization.

## Abstract

Here we propose a waveguide-integrated germanium plasmonic photodetector that is based on a long-range dielectric-loaded surface plasmon polariton waveguide configuration. As this configuration ensures a long propagation distance, i.e., small absorption into metal, and a good mode field confinement, i.e., high interaction of the electric field with a germanium material, it is perfect for a realization of plasmonic germanium photodetectors. Such a photodetector even without optimization provides a responsivity exceeding 1 A/W for both wavelengths of 1310 nm and 1550 nm. To achieve such a responsivity, only a 5 {\mu}m-long waveguide is required for 1310 nm and 30 {\mu}m-long for 1550 nm. With optimization this value can be highly improved. In the proposed arrangement a metal stripe simultaneously supports a propagating mode and serves as one of the electrodes, while the second electrode is located a short distance from the waveguide. As a propagating mode is tightly confined to the germanium ridge, the external electrode can be placed very close to the waveguide without disturbing it. As such, the distance between electrodes can be smaller than 350 nm which allows one to achieve a bandwidth exceeding 100 GHz. However, as most of the carriers are generated inside a distance of 100 nm from a stripe, a bandwidth exceeding 150 GHz can be achieved for a bias voltage of -4 V.

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Source: https://tomesphere.com/paper/1906.04676