We present a methodological contribution to the modeling of waveguide photodetectors for silicon photonics. This technology specializes in making silicon-compatible photonic devices and thus takes advantage from state-of-the-art MOS technology. After a general introduction to photodetectors, the thesis presents simulation results obtained with an approach not conventionally applied to these devices, validated against experimental measurements provided by the group’s research partner Cisco System. We use commercial 3D multiphysics simulation tools to solve first the optical problem (with FDTD) and then the electrical problem (with drift-diffusion). In order to assess the dynamic response of the devices, rather than using a conventional small-signal approach, we have performed transient simulations taking into account the temporal variations of the optical signal.