Waveguide-coupled germanium lateral uni-traveling-carrier photodetector for coherent applications at 130 Gbaud and beyond

We propose a novel waveguide-coupled germanium lateral uni-traveling carrier photodetector (L-UTC PD) structure, which offers tremendous potential for coherent communication applications at 130 Gbaud and beyond. This PD structure is very simple and can be easily fabricated in a commercial silicon photonics (SiPh) foundry. The fabricated L-UTC PD has a very low dark current (~4.2 nA), a high responsivity (~0.66 A/W@1550 nm) and a small capacitance (<14.6 fF). Moreover, the L-UTC PD exhibits excellent tolerance to high optical input power, with a 3-dB bandwidth exceeding 67 GHz, even at a high photocurrent of 3.0 mA.