Channel length

[bfazi]

Hi,
I have a question about the channel length when we build a transistor in VNL. As I know we should add some screening lengths to the central region to get a precise result so the channel length is equal to the central region plus screening lengths? or the channel length is only equal to the central region?
I attached a picture about graphene nanoribbon FET to clarify my question.

Thanks

[Anders Blom]

The entire central region screens the electrostatic potential. If you by channel length mean the points between which the potential drops (i.e. where the bias is applied), then it's the same, also across the entire central region.

You may be a bit confused by the picture posted, where it looks like the central region is the part between the screening regions - that is not the case. Scroll down to Fig. 3 in  this tutorial http://docs.quantumwise.com/tutorials/atk_transport_calculations/atk_transport_calculations.html to get a better picture.

Note that ATK < 2008 and some other codes do this differently.