Fig. 3

The optimal doping level and thickness of charge layer for different multiplication layer. Solid line: w _m  = 300 nm. Dashed line: w _m  = 500 nm. Dot line: w _m  = 700 nm. Presents the calculated values of charge layer (doping level and thickness) by the formula while the field of absorption layer is suitable. The thicknesses of the multiplication layer are 300, 500, and 700 nm. When the thickness of the multiplication layer is certain, we can use the formula to find the optimal doping level and thickness of charge layer