Theoretical Study Of Electronic Transport Characteristics Of Carbon Nanotube Field Effect Transistors

Because of its superior performance, carbon nanotube has been applied in moreand more fields since it was found. More and more researches have shown that: thecarbon nanotubes have more extensive application prospect in nanoelectronics. Sincethe carbon nanotubes field effect transistor can replace the silicon-based field effecttransistor, so that its future application in nanometer integrated circuit becomespossible.This paper describes the basic characteristics of carbon nanotube firstly,and thenanalyzes the modeling of carbon nanotube field effect transistors based on non-equilibrium Green’s theory.the main work is to study the influence of the channellength and source/drain doping content on the transport characteristics. Meanwhile,toimprove the carbon field effect transistor device performance improvement, aheterogeneous-dual-metal-gate carbon field effect transistor is proposed.This paper deduces the corresponding physical the Green’s function’s expressionof carbon nanotube field effect transistors(CNTFET) in real space and the mode spaceby quantum modeling based on the non-equilibrium Green’s function theory. Thetransport behavior of CNTFET was modeled and calculated by solving the selfconsistent Poison and Schrodinger equations within the non-equilibrium Green’sfunction framework.Based on the theory of non-equilibrium Green’s function, we firstly evaluate theinfluence of the channel length and source/drain doping content on the transportcharacteristics, including on-and off current, on-off current ratio, threshold voltageswing, and ambipolar conductance. The simulated results show that the transportbehavior depends weakly on a channel length longer than15nm.As the channel lengthdecreased from15nm,the on-current slowly increased, accompanied by the decreasesof threshold voltage and on-off current ratio, the increases of off state leakage currentand sub-threshold swing, and a more serious ambipolar conduction or short channeleffect. We suggest that an appropriate reduction of the source/drain doping contenteffectively weaken the short channel effect of CNTFET devices.To improve CNTFET device performance, a heterogeneous-dual-metal-gateCNTFET is proposed. The results indicate that when the same operating voltage isapplied, a heterogeneous-dual-metal-gate device has a larger on-state current than single-metal-gate device, it also can suppress the drain induction barrier lower effect,hot electron effect and ambipolar conduction behavior. Except that it can effectivelyovercome the deficiency of existing research on improving CNTFET performance atthe expense of reducing the on-current, more importantly, can improve the electrontransport efficiency, thereby improving the characteristic frequency and reducing thedelay time of the device, which will be of benefit to CNTFET application inhigh-speed/high-frequency circuit.