Theoretical Study Of Electronic Transport In Carbon Nanotube Field-effect Transistor

Carbon nanotubes have unique mechanical, electrical and optical properties, and they exhibitbroad application prospect. According to their symmetric structure, single-walled carbon nanotubescan be metal or semiconductor. The electronic transport in carbon nanotubes is typical ballistictransport, it has an advantage of a large current density, small resistance, large carrier mobility andgood heat conduction. Single-walled carbon nanotubes have been used in many laboratories athome and abroad to fabricate field effect transistors(CNFET). They will be applied to nano-scaleelectronic integrated circuits, and lead to the miniaturization of electronic industrial products andthe leap of the performance. But, the experimentalists have observed random-telegraph-signal(RTS) noise due to a single defect in carbon nanotube field-effect transistors, and found thatsometimes the amplitude of the RTS noise in CNFETs is even larger than that in silicon-basedtransistors. It is known that the superposition of RTSs due to many defects in the gate oxide willlead to low frequency1/f noise [P. Dutta and P.M. Horn, Rev. Mod. Phys.53,497(1981)].Theelectrical noise problem hinders in some way the industrialization process of carbon nanotubefield-effect transistors. Therefore, understanding the RTSs due to individual defects in CNFETs isimportant for designing CNFETs with low noise.In this thesis, non-equilibrium Green function theory is applied to evaluate the current through aCNFET and investigate systematically how the random-telegraph-signal noise depends on thecarbon nanotube radius, gate oxide thickness, and dielectric constant of gate oxide. And then, wecalculate the random-telegraph-signal noise due to a single defect in composite gate dielectrics, soas to find a way to reduce the noise. The calculation results may be used as a theoretical referencefor designing CNFETs with low noise. The improvement of CNFET performance will speed upthe industrialization process of CNFETs.