Fringe field effect

[ramkrishna]

Hi,
In the current NEGF, does it consider the effect of fringe field of a gated device? If so, can you please let me know the formalism of that?

Thanks
Ramkrishna

[Jess Wellendorff]

Could you explain what you mean by "fringe field"?

[ramkrishna]

Normally the flux lines inside the gates are uniform and parallel in MOSFETs. But at the edges, the flux lines are not straight and bend slightly upward due to the geometry. This extended field (nonlinear) at the sidewall is the fringing field. In the literature, there are many references of fringe field, especially in the context of short channel effect in MOSFETs.

[Jess Wellendorff]

Electrostatic gates in ATK NEGF are regions in space with a constant potential. If the fringe field is a purely electrostatic effect, then yes, it should be included. I have attached an image of the electrostatic difference potential for a gated nanoribbon, with gate potentials 0 V below and 1 V above.

[ramkrishna]

Hi Jess,
Thank you for the clarification. I have another query on this. Is it possible to calculate this fringe capacitance?

Thanks
Ramkrishna

[Petr Khomyakov]

Do you mean whether it is possible to calculate it in ATK? There is no such a feature in ATK. But you may use, in principle, the electrostatic difference potential (EDP) from ATK for the capacitance calculation in a customary python script if you know the definition of this capacitance in terms of EDP.