The Terahertz Characteristics Of New Type Nanometer Field-effect Transistor

Using non-equilibrium Green’s function and Poisson equation, model of description theelectrical properties of carbon nanotube and graphene FET is built. Then, based on gatestructure and channel engineering, self-consistent calculation of FET is performed. Then, thestudy is expanded to Terahertz. Discussion of Terahertz radiation and detection based on thetheory of fluid dynamics is presented. The main work of this paper can be summarized as:Firstly, a brief introduction of structural characteristics, electrical properties, applications ofcarbon nanotube and graphene are presented, and using non-equilibrium Green’s function andthe Poisson equation, model of calculating electrical characteristics of the FET is built.Secondly, based on the advantages of hetero-gate and foundation of channel engineering,electronic properties of both linear doped carbon nanotube FET and lightly drain dopedgraphene nanoribbon FET are compared with ordinary structure. The results show thatcompared with conventional doped structure, linear doping has smaller leakage current and offcurrent, greater average electron velocity. Lightly drain doping makes the electric potentialfrom source and drain to gate change flatly, reduces the possibility of band-to-band tunneling,increases the ability of the gate controlling and the transmission efficiency, results in greatertransconductance, higher cut-off frequency, lower switching time and sub-threshold swingThen, high-frequent characteristics of underlap gate FET are discussed, and the comparisonof single-and triple-material-gate are made. The results show that underlap gate reduces theelectric field from the source and drain to the metal gate, results in smaller gate capacitance,increases cutoff frequency to Terahertz level, shorten relaxation time. Also, desirable cut-offfrequency and current ratio can be obtained by setting reasonable gate or underlap length.Finally, based on the theory of fluid dynamics, Terahertz radiation and detection modelusing FET is built. Threshold condition of stable plasma wave oscillation and analysis ofinfluence factors of Terahertz detection are presente. The results show that, for resonantresponse, the peaks appear when signal frequency is equal to intrinsic frequency, fornon-resonance, the response is a smooth curve.