(Invited) Si Waveguide-Integrated High-Speed Ge Photodetector

Abstract

We present a Si waveguide (WG)-integrated high-speed Ge-PD (photodetector), which shows high speed of 50 GHz bandwidth with small footprint. First, we compare Si WG-integrated p-i-n and Schottky Ge PDs, which show very low dark current density with high efficiency. In addition, we study two types of p-i-n Ge-PDs, which are evanescently coupled and butt-joint coupled with the Si WGs. The optimized evanescently coupling type of a p-i-n Ge-PD shows good photoresponsivity of 0.8 to 1.0 A/W and low dark current density of 0.6 nA/μm2. It shows 50 GHz bandwidth at Vdc more than 3 V, and 30 GHz at 0 Vdc in case of 10 μm optical coupling length. Furthermore, we develop a butt-joint type p-i-n Ge-PD and achieve 46 GHz bandwidth and high-efficiency with only 5μm optical coupling length.