A time-delay equivalent-circuit model of ultrafast p-i-n photodiodes

A time-delay equivalent-circuit model of ultrafast p-i-n photodiodes (PDs) is proposed to describe the operation at high-input power levels. This model includes both the carrier transit-induced time-delay effect and stored charge effect of p-i-n PDs in high-power operation. These effects were represented as a linear RC circuit and capacitance, respectively, both combined in parallel to a voltage-controlled current source. The validity of this model was confirmed with good curve fitting to the measured optical-frequency responses of an ultrafast side-illuminated p-i-n PD.