Modeling of the current-dependent 3-dB bandwidth in modified uni-traveling-carrier photodiodes

A physics-based model is proposed for the current-dependent 3-dB bandwidth in Modified Un-Traveling-Carrier Photodiodes. In the effective circuit model of the photodiodes, the junction resistance and capacitance are extracted from the real and imaginary parts of the near-DC complex junction impedance; the effect of carrier transit time across the absorber and electron transition layer is evaluated by the frequency-dependent AC conduction current output to the electron transition layer and the average induced AC electron current across the electron transition layer, respectively. The simulation results by this model agree well with the measurements.