I believe that the badwidth is not a linear function of voltage or electric fields. There are other factors that impacts the badwidth, in addition to the transient behavior and charges. Khash has replied in this post: How to test the saturation performance of the photodiode?
The best way is to find a benchmark example for verification. 3D and 2D is different even though the device size is the "same". The distributed RC may not be the same.
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