Scaling Effects on the Plasmonic Enhancement of Butt-Coupled Waveguide Photodetectors

We employed 3D opto-electrical simulations to study the scaling effects of a plasmonic structure on the optical performance of butt-coupled waveguide photodetectors by placing an Ag stripe on top of the intrinsic region. It is found that cutoffs which are limited by carrier drift in the high-field region of the non-plasmonic device improve with longer and wider stripe, while the metal thickness has only little impact. Furthermore, the diffusion and low-field drift limited cut-offs can be eliminated with metal stripes longer than 400 nm.

I. Introduction

Monolithically integrated photodetectors (PDs) with ultrafast and broadband detection are required for optical links in data centers. Their detection speed can be improved by structure miniaturization to reduce the carrier transit time. However, further down-scaling of conventional PDs is restricted by the diffraction limit. Plasmonic devices become attractive due to their ability to overcome this bottleneck, and different types of plasmonic PDs have been recently reported [1] [2]. In this work, we first study the physical mechanisms limiting the response of a previously designed non-plasmonic butt-coupled waveguide photodetector (WGPD)[3], and then explore their impacts on the optical performance when scaling the plasmonic structure. All investigations are conducted using coupled 3D opto-electrical simulations with Sentaurus Electromagnetic Wave (EMW) Solver [4] for FDTD calculation and Sentaurus Device [4] for electrical transport. The Ag/intrinsic region (i-region) interface is assumed as ideal Schottky type (barrier height 0.6 eV) without image-force lowering.