An Equivalent Circuit Model for a Ge Waveguide Photodetector on Si

We present an equivalent circuit model with improved accuracy for 1.5-μm germanium waveguide-type vertical photodetectors on a silicon-on-insulator substrate. Our model consists of passive circuit components, two current sources for photogenerated carrier transports, and one noise current source. Model parameters are extracted from electrical S-parameter measurements, TCAD simulations of photodetection frequency responses, and noise measurements. The resulting equivalent circuit model accurately provides photodetection frequency responses at different bias voltages and should be of great use for high-performance optical receiver circuit design.