Electrostatic difference potential vs coordinate of c direction

[ocdor]

Dear ATK experts:
                   In ATK manual, I have seen the corresponding reletionship between Electrostatic difference potential with coordinate of c direction, like the enclosed picture. So, it is not include the left and right electode?

[Petr Khomyakov]

That is correct. The EDP plot of a device does not show the potential in the electrode regions, only in the central region. If you have chosen the central region is large enough (as it should be), the potential in the left (right) electrode extension, which is part of the central region, is to be virtually the same as the potential in the left (right) electrode region. In other words, the central region must be longer than the screening length.