Photonic crystal enhanced Germanium photodetector on a CMOS compatible SOI platform

Germanium is the preferred photodetector material at C-band due to its broadband detection range and easy integration with Silicon on Insulator platforms. However, current non-resonant broadband Germanium detectors result in long device lengths, thus resulting in a low RC bandwidth. Smaller resonant detectors provide low parasitic constants at the expense of narrow optical bandwidth. This work presents a waveguide-coupled germanium detector on top of a lattice-shifted photonic crystal waveguide, operating at a broadband slow light mode. Slow light enhances light absorption inside a 14μm long Germanium stripe, resulting in a large responsivity of 0.47A/W at 1V reverse bias and a dark current of 82nA. The device also maintains high responsivity over a bandwidth of 30nm. This work provides a path to design small footprint, broadband, and low dark current Germanium detectors on a CMOS-compatible platform.