Learning Forum

[HAOYU LIU]

I want to test the bandwidth of the  photodiode model used in one paper, and I follow the video of lumerical transient PN junction bandwidth. I think I have set the model and parameters properly, but the results and some phenomenons are strange, the bandwidth decreases as the bias voltage increase, obey the paper. The bandwidth decreases when I use the grading doping in the absorption layer which can produce electric field to accelerate the electrons (the structure is uni-travelling-carrier photodiode). Also, the bandwidth increases as I decrease the mobility of the electrons, very strange. And I find that the carrier life of the Ge (absorption layer, p type) will affect a lot on the bandwidth. I don't know why. I think this transient is mainly about the transit time limited bandwidth because I didn't add additional R or C in the boundary conditions. T he electrical field, bias voltage, carrier mobility and layer structure should affect the bandwidth but the simulation results seems obey some principle. How to fix these problems?