The influence of nonlinear capacitance and responsivity on the linearity of a modified uni-traveling carrier photodiode

Third-order intermodulation distortion in an InGaAs/InP charge compensated modified uni-traveling carrier photodiode is characterized using a two-tone setup. At 310 MHz modulation frequency the third-order local intercept point (IP3) reaches 52 dBm and remains above 35 dBm up to 21 GHz. Voltage dependent nonlinear responsivity is found to be the limiting factor for the IP3 at low frequency, while the voltage and photocurrent dependent nonlinear capacitance is responsible for the decreasing IP3 with increasing frequency. The physical origins of the nonlinear responsivity and capacitance are investigated.