25Gb/s normal incident Ge/Si avalanche photodiode

We developed world first 25Gb/s normal incident germanium silicon avalanche photodiode (Ge/Si APD) in a CMOS commercial foundry. The vertically illuminated Ge/Si APDs have a large 3-dB bandwidth (>18GHz) at a high gain (M=8) which is suitable for 100GBASE-ER4 application.