High-Speed and High-Power Ge-on-Si Photodetector with Bilateral Mode-Evolution-Based Coupler

We propose a germanium-on-silicon photodetector with a bilateral mode-evolution-based coupler. Based on the double-sided mode-evolution, the light illuminates the whole Ge absorption region uniformly, which alleviates the space-charge effects and decreases the saturation effects. The simulated results show 53% more photocurrent generation and more than 19 times the opto-electrical bandwidth than conventional butt-coupled photodetectors under high-power illumination. In addition, an equivalent circuit model is presented to investigate the limiting factors of bandwidth. A genetic algorithm is used to extract the parameter values of components in an equivalent circuit by fitting the simulated two-port S22 parameter. The results show significant improvement in high-power and high-speed performance compared with conventional butt-coupled detectors