Effective carrier lifetimes of Si modulators based upon a lateral p-i -n structure were measured using the reverse-recovery method. Modulators of two different waveguide dimensions were characterized using this approach. Two additional lifetime measurement methods were used to check against this method and showed consistent results. Finally the physical meaning of this measured effective carrier lifetime was discussed in reference to its relationship with the diode transit time, surface recombination velocity and the bulk carrier lifetime.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.