Electronic Transport Properties Of Carbon Nanotube Field-effect Transistors

In this work, the electronic transport properties of carbon nanotube field-effect transistors arestudied using non-equilibrium Green’s function method in the framework of the full-quantummechanical model. It may provide theoretical guidance for the design and optimization ofnanoelectronic devices which based on carbon nanotube field-effect transistors.Firstly, it deduces the corresponding physical the Green’s function’s expression of carbonnanotube field-effect transistors in real space and the mode space by quantum modeling based onthe theory of non-equilibrium Green’s function. Through calculating the electrical properties of thecarbon nanotube field-effect transistors by the mode space method, it finds that the electricalproperties of carbon nanotube field-effect transistors are similar with that of Si-based MOSFETs,such as linearity, saturation and cutoff characteristics; the local-density-of-states spectra and theelectron density spectrum can clearly see the phenomenon of band gap, quantum interferometer, andquantum confinement.Secondly, it proposed two new structures of the carbon nanotube field-effect transistors whichare dual-material-gate carbon nanotube field-effect transistors with underlap gate andtriple-material-gate carbon nanotube field-effect transistors with underlap gate. Compared with thecarbon nanotube field-effect transistors, it finds that these carbon nanotube field-effect transistorscan suppress the short channel effect effectively, have a better control ability of gate, optimize theperformance of the on/off current ratio, and the cutoff frequency reaches up to a few THz.Finally, the electrical properties of the quasi-one-dimensional carbon nanotube system havebeen studied based on the nonequilibrium Green’s function(NEGF).The calculation results showthat when the same continuous square pulse signal is injected into the lead, a greater couplingbetween the electrode and the carbon nanotubes causes a steeper initial rise in current. When asinusoidal signal of a low frequency is injected into the lead, the current curve becomes irregular.