On the frequency response of a resonant-cavity-enhanced separate absorption, grading, charge, and multiplication avalanche photodiode

In this article the frequency response of a resonant-cavity-enhanced (RCE) separate absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode (APD) has been investigated. This study on APDs includes the development of a model for the avalanche buildup of carriers including the dead-space effect. In this model, the carriers are characterized by their energy and position in the region of multiplication. The excess energy of the carriers above threshold are assumed to be equally distributed among the carriers after impact ionization. The analysis shown in this article can be used to study the frequency response of the APD for a wide range of reverse bias voltages. For low bias voltages, an analytical expression has been derived to study the emission of carriers from the interface trap. The delay due to diffusion of photogenerated carriers from the undepleted region of the absorption layer and the low velocity of carriers at low field have also been considered. The model is used to calculate gains at different biases and bandwidth at different dc gains. The results show good agreement with published experimental data on a RCE SA(G)CM APD.