The high‐speed performance of InGaAs interdigitated metal‐semiconductor‐metal (M‐S‐M) photodetectors illuminated with 1.55 and 1.3 &mgr;m wavelength radiation is modeled using a two‐dimensional transit time calculation. Excellent agreement is found with the experimental pulse response of detectors with interdigital spacings of 2 and 3 &mgr;m. We study the dependence of the bandwidth on the device dimensions, and also examine the quantum efficiency. The results should aid the design of InGaAs M‐S‐M detectors with the optimum combination of bandwidth and efficiency for a given application.