An Extensive Large Signal Equivalent Circuit Model of GaAs-PIN Photodiode

Based on the variation trend of the depletion layer of GaAs-PIN photodiode (PD) under different optical power and reverse bias voltages, an extensive large-signal equivalent circuit model that characterizes PD in non-punch-through and punch-through states is proposed in this article. According to the analysis of the PD’s depletion layer variation, the nonlinear parameters of the model are described by exponential function and Gaussian function. To verify the reliability of equivalent circuit model, on-chip measurements were performed on PIN-PD fabricated by commercial GaAs process, and the measured
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and reflection coefficient agree with the proposed model simulation results well. Furthermore, using the proposed model for simulation with CAD tools shows that reducing junction capacitance has potential in improving PD output power and gain flatness. At the same time, the model provides a certain reference for selecting bias condition in the design of the PD matching network and fabricating PD with high power output.