Fig. 4

Tunneling process and charge density change in the multiplication and absorption layers. Presents a schematic diagram of tunneling process in the device. If a sufficiently high electric field exists within the absorption layer, the local band bending may be sufficient to allow electrons to tunnel. When the absorption layer has a breakdown tunneling, the positive charge in absorption increases and the negative charge in the multiplication and charge layers increases. Thus, ρ is not equal to the dopant ion charge density in the depletion layer while the tunneling effect appears