%0 Journal Article %J IEEE Trans. Nanotechnol. (USA) %D 2005 %T Method for predicting fT for carbon nanotube FETs %A Castro, L C %A John, D L %A Pulfrey, D L %A Pourfath, M %A Gehring, A %A Kosina, H %K capacitance;carbon nanotubes;electric admittance;equivalent circuits;field effect transistors;nanotechnology;Poisson equation;SCF calculations;Schrodinger equation;semiconductor devices; %P 699 - 704 %U http://dx.doi.org/10.1109/TNANO.2005.858603 %V 4 %X A method based on a generic small-signal equivalent circuit for field-effect transistors is proposed for predicting the unity-current-gain frequency fT for carbon-nanotube devices. The key to the useful implementation of the method is the rigorous estimation of the values for the components of the equivalent circuit. This is achieved by numerical differentiation of the charges and currents resulting from self-consistent solutions to the equations of Schrodinger and Poisson. Sample results are presented, which show that fT can have a very unusual dependence on the gate-source bias voltage. This behavior is due mainly to the voltage dependence of the transconductance and capacitance in the presence of quasi-bound states in the nanotube %Z carbon nanotube devices;FETs;small-signal equivalent circuit;field-effect transistors;unity-current-gain frequency;numerical differentiation;charges;currents;self-consistent solutions;Schrodinger equations;Poisson equations;gate-source bias voltage;transconductance;capacitance;quasi-bound states;nanotechnology;quantum effect semiconductor devices;quantum wires;semiconductor device modeling;C; %9 article