As in case of capacitance calculation for super-capacitor the CV charge discharge method is popularly used. Can the similar method be implement to calculate the capacitance for graphene based FET.
If yes then how?
If no than why?
Dear Professor Kapil Bhatt ,
I believe that it is possible. Pretty frequently we (our lab) measure capacitance of a MIS (metal-insulator-semiconductor) capacitor using CV method (we study charge effects in the structures under high fields; a lot of our papers dedicate to that). Of course we measure the capacitance for the accumulation mode. I see no reason how graphene layer can significantly influence onto the measurements. And, because of it is a FET, you should connect source and drain together to obtain two electrodes. I hope this will be helpful.
Best regards,
Dmitrii
Thanks Prof. Andreev for your suggestion. One of mine colleague said that this method is applicable to super-capacitor only not for FET like device due to the leakage current involves. But we are not sure still and not found any article in support of this to measure the capacitance of Graphene based FET via charge discharge method.
Dear prof. please recommend any article related to this if any?
Thanks and regards!!!
Kapil Bhatt The capacitance can be calculated using two electrodes sandwiched with dielectrics. The FET geometry has three electrodes. You couldn't easily measure the capacitance since currents can leak through the third electrode if two electrodes are used. We always make separate devices to measure the dielectric constants via a two electrode sandwiched structure.
Dear Professor Kapil Bhatt ,
Just avoid high voltages (high-fields more precisely) in order to not allow the tunnelling (leakage current). In case of the tunneling (Fowler-Nordheim, Frenkel-Poole, etc.) some tunneling charge is trapped in bulk of the insulator what results in change of charge state and, subsequently, in change of voltage across MOS capacitor when measuring by CV. These effects are well discussed in https://www.wiley.com/en-ru/Physics+of+Semiconductor+Devices,+3rd+Edition-p-9780471143239 (see the chapter dedicated to MOS capacitor which one you will obtain by connecting two electrodes of the FET together).
I hope this will be useful.
Best regards,
Dmitrii
Dear Kapil,
welcome,
I would like to add to the colleagues above that you raised an important point which is the leakage of the charges through the capacitor which may affect the charging discharging process. If the leakage current is much smaller than the capacitive current then you can use the charging discarding method for measuring the capacitance of the MOS capacitor. If you make the scanning with relatively high speed you also increase the capacitive current relative to the leakage current. If this method has unacceptable accuracy then you can use AC impedance measurement using RLC meters or bridge. For the details of the measurements please see the link: Article Capacitance and conductance of ZnxCd1-xS/ZnTe heterojunctions
Best wishes
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