100  GHz bandwidth ultra-thin germanium photodetectors with high responsivity on a 300  mm silicon photonics process

Germanium photodetectors (Ge-PDs) are key components in silicon photonics (SiPh) to enable high-speed optical communications for various applications. Several works have been reported to improve the bandwidth, quantum efficiency, and manufacturing process of Ge-PDs. However, a significant trade-off between bandwidth and responsivity remains a major challenge in developing high-performance Ge-PDs for large-scale silicon photonic integrated circuits. Here, by co-optimizing the chemical mechanical polishing (CMP) process and device structure, ultra-thin Ge-PDs with high 3 dB bandwidth have been achieved. The dimensions of the Ge region and doping areas have also been optimized to attain a high-bandwidth, high-quantum-efficiency product. Consequently, we demonstrate lateral-PIN Ge-PDs with a high bandwidth of up to 100 GHz, 1.05 A/W responsivity at 1550 nm and <20nA dark current on 300 mm CMOS silicon-photonic process. Our work demonstrates that high-performance Ge-PDs with a simple fabrication process are feasible, which paves the way for developing next-generation 200 Gbaud intensity-modulated direct-detection (IMDD) and coherent optical systems.