the relationship between the dielectric constant and the transport properties

[dong0216]

Hello everyone，
        I had a problem when I calculated the transport properties. The transmission spectrum of the field effect transistor with or without a dielectric layer is different, but the parameters are the same. I want to know how does the dielectric layer affect the transport properties and is there a formula describing the relationship between the dielectric constant and the transport properties?
       Looking forward to your reply. Thank you.

[Petr Khomyakov]

Hello everyone，
        I had a problem when I calculated the transport properties. The transmission spectrum of the field effect transistor with or without a dielectric layer is different, but the parameters are the same.

But what is the actual problem? The transport properties should depend on the dielectric properties of the insulating spacer between the channel and gate electrode, because one gets different capacitance for the systems with different dielectric constants of the spacer. To understand physics of this, one could imagine a planar capacitor with a fixed bias applied to the capacitor planes for vacuum (epsilon=1) and some dielectric (epsilon <> 0). Using higher-epsilon dielectric increases the capacitance of the system, https://en.wikipedia.org/wiki/Capacitor, C ~ epsilon.

[dong0216]

Thanks for your reply. I'm sorry for not being able to clearly explain my problem. Here's my question that  the calculation of the transmission spectrum are different between when I do not add dielelctric and the gate voltage, and  when I add dielectric layer and the gate voltage, but set the gate voltage is 0.  I don't know why and  I am not very clear that how to influence the transport properties of dielectric layers. Is there a formula to describe it?  Looking forward to your reply.

[Petr Khomyakov]

You do change the total capacitance of your device when introducing a dielectric spapcer, changing the device IV-characteristics, see this paper IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 54, NO. 12, DECEMBER 2007 for more details.