A model for the performance analysis and design of waveguide p-i-n photodetectors

A model to investigate the frequency response of waveguide (WG) p-i-n photodetectors (PDs) is presented. The model is based on the 2-D position-dependent distribution of carriers in the device and the results show that the contribution to the total current mainly comes from a small length of the PD measured from its input end. The effect of carrier trapping at a heterointerface has also been considered to study the frequency dependence of the photocurrent at low-bias voltages. The frequency response and bandwidth obtained from the model are in good agreement with published experimental results. A simplified and approximate relation for the fiber-to-WG coupling efficiency has also been used to calculate the overall quantum-efficiency of WGPDs. Then, the effect of WG geometry on the bandwidth-quantum efficiency product has been analyzed and some results on the optimum design of a WG p-i-n PD for maximum bandwidth-quantum efficiency product have been tabulated.