Why does carrier density in GFET and GFET(reduced the gate) is the same?

[ocdor]

Dear ATK experts:
            Why does carrier density in GFET and GFET(reduced the gate) is the same?Thank you for your answer!

[Petr Khomyakov]

Could you enclose the scripts and log files related to these calculations?

[ocdor]

Sorry,i didn't find your reply untill this morning.the log and script are enclsoed.Thank you !

[Petr Khomyakov]

Why would you expect a significant change in the electron density? It is more important to verify if there is any effect of gating on the transmission spectrum.

I would also try increasing the metal gate thickness from 0.5 Angs to something like 5 Angs. I am not sure that the dielectric spacer thickness of 3 Angs is realistic as well.

[ocdor]

Of course, effect of gating on the transmission spectrum is important.  My purpose is to study the change of transport properties of graphene device by varing gate voltage, I think that the ralationahip between fermi level and charge density is also  important. It  seems unrealistic that charge density is not changed while  fermi level is obviously changed. Why?
Thank you!

[Anders Blom]

How do you know it's not changed? Did you calculate the difference? Just looking at the colors in the plot will not be very quantitative. I could say one plot is slightly more purple than the other, but the only real way to check is to subtract them from each other.

[Petr Khomyakov]

I do not say that charge density is not important for your study, but my suggestion is to first check if there is any effect of gating on the transmission spectrum, as it is likely to be more sensitive to the applied gate voltage than the charge density. If there is no effect on the transmission, it would then mean that there is something wrong with the calculation setup. The charge density might not be a good quantity for this check because the gate-induced changes in the density can be rather small to be visible on the graph you have posted.

[ocdor]

Thank you for your reply! I understand what you mean.