Miniaturized waveguide-integrated p-i-n photodetector with 120-GHz bandwidth and high responsivity

A low-capacitance waveguide-integrated photodiode on InP with a minimized absorber length is presented. In order to maintain a high quantum efficiency, an optical matching layer exploiting mode beating effects is employed. Its optimization leads to a twofold enhanced external responsivity of 0.5 A/W at 1.55-μm wavelength in accordance with simulation. The reduced p-n junction capacitance enables 3-dB bandwidths up to 120 GHz mainly limited due to carrier transit time effects.