Optimization of electrode distance and 2D material coverage for PdSe2-based waveguide-integrated photodetectors

Silicon-based waveguide-integrated photodetectors, leveraging their distinct advantages, have become crucial components in integrated photonic circuits. Despite achieving combined designs of two-dimensional materials and silicon waveguides, understanding the underlying mechanisms and optimizing structural designs remains challenging. In this study, we systematically investigated the impact of electrode distances on the optical loss and photoelectric response of PdSe2-based strip, rib, and slot waveguide-integrated photodetectors. Optimal electrode distances were determined, leading to significant enhancements in responsivity. Specifically, our devices demonstrated high responsivity values of 9.24 A/W (strip), 3.34 A/W (rib), and 4.52 A/W (slot) at 1550 nm. These results represent remarkable enhancements of 481%, 237%, and 267%, respectively, compared to the initial unoptimized electrode configurations. Additionally, we found the slot waveguide-integrated photodetector achieves 34% of absorption saturation with PdSe2 coverage of approximately 10 mu m, while the rib waveguide enables 70% absorption (not yet saturated) with PdSe2 coverage of 50 mu m. Furthermore, we explored the effect of input power on the performance of these photodetectors, finding that lower input optical power yields higher responsivity and external quantum efficiency (EQE), especially for slot waveguide-integrated photodetectors. Additionally, these detectors exhibit fast optical response rates across the optical communication O to U bands, with strip, rib and slot waveguide-integrated photodetectors demonstrating 3 dB bandwidths of 23.10, 14.49, and 14.86 GHz, respectively.