An equivalent circuit model and biasing effects over the gain and bandwidth of waveguide avalanche photodetectors (WG-APDs)

Waveguide photodetectors (WG-PDs) are a promising candidate to overcome the trade-off between the quantum efficiency and bandwidth in conventional photodetectors. In this paper, complete physics and circuit models of waveguide-separated absorption grading charge multiplication-avalanche photodetector (WG-SAGCM-APD) are presented. In this model, the effects of the biasing, doping and the thicknesses of the different layers of the photodetectors, the parasitic of the photodetector and the velocities of photogenerated carriers over the multiplication gain and the bandwidth of the photodetectors are studied and taken into consideration. The results obtained the presented model of WG-SAGCM-APD are compared with published experimental results and a better agreement than with a previous model is obtained. The presented circuit model is generic and can be applied to different structures of WG-APDs.