I am doing an analysis of Si and GaAs photodetector by simulation using TCAD tools. I need to characterize the device to get photocurrent value and transit time for various doping concentrations using Simulator MEDICI. I had already done the simulation however I am not sure my result is correct or not. So, I need to compare my simulation result with the theory. The problem is I still cannot find the exactly fact about it. I want to know the effect of various doping concentration toward the performance of Silicon (Si) and Gallium Arsenide (GaAs) photodetector. As in fact, whether high or low doping concentration will result in good performance of photodetector? What is the effect of doping concentration in photodetector mechanism? For the information, I used Arsenic as the dopant.