I am working with Cylindrical GAA finfet so I need to plot the threshold vs channel length curve and I am not getting how to find it so anyone can help me ?
In order to get threshold voltage you have to calculate ID versus VGS for a specific value of VDS in the saturation region. In this case one plots SQR ID versus VGS and extrapolates it to zero current. The interception point VGS will be the cut off value required.
This can be repeated for all required value of the channel lengths.
Finally one plots the the threshold value Vt = VGS cut off as a function of the channel length L.
There may other methods depending on how do you measure Vt, the threshold value.
There are various definitions of threshold voltage for FETs. for example in the TFETs we define the threshold voltage as a gate voltage at which the drain current reaches to 1E-7 A/um. You can first calculate the threshold voltage for each channel length with the help of the "extract" command and then draw the Vt-Lg curve.