| In this thesis, an extensive study of various aspects of modeling of high speed photodetectors is presented. This study concentrates on the modeling and the optimization both of resonant cavity enhanced photodetectors (RCE-PDs) and waveguide photodetectors (WGPDs) because they are considered to be the leading candidates to overcome the bandwidth-quantum efficiency trade-off of conventional photodetectors.; For both RCE- and WG-PDs, we have concentrated on PIN-PD and separated absorption graded charge multiplication avalanche photodetector (SAGCM-APD) structures.; In this study, a physical model for each type of these photodetectors is presented. This includes the modeling of both the time and frequency responses as a function of their dimensions and material parameters. Gain-bandwidth characteristics are also studied for the two types of APDs.; Further, calibrated circuit models for these high speed photodetectors are presented showing the dependence of the circuit model's transfer function on the materials, dimensions and multiplication gain (in the case of APDs) of the photodetectors. In these circuit models, the photodetector can be applied as a lumped circuit element in any circuit simulation program. For all the photodetectors studied, predictions of the circuit models are compared with published experimental results and good agreements were obtained.; The parasitics effects on RCE-PDs and WG-PDs are carefully studied because they can significantly degrade their performance. The effects of the parasitics on both of the time and frequency responses are studied. It is also shown how to compensate for the performance degradation from these parasitics.; Finally, optimizations are applied to these photodetectors for different areas and multiplication gains to get the optimal values of the thicknesses of both of the absorption and multiplication layers and also the optimal values of the inductor that may be added to improve the photodetector's performance. In this way, optimized designs of high performance photodetectors can be realized. |
