Switching Characteristics And High Frequency Characteristics Of Graphene-nanoribbon-based Nanostructure

Graphene, which is consist of a single atomic layer of carbon atoms，is confirmed to havemany unique chemical properties, physical properties, and electrical properties, such as lowimpedance and high strength and high thermal characterization, is an ideal material fornano-electronic devices. The electronic transport properties of graphene nanoribbon FETs(GNRFETs) are investigated based on non-equilibrium Green’s functions (NEGF) solvedself-consistently with3D-Poisson’s equations. Then we investigated the major factors whichaffecting on the performance of the devices, and provide an effective solutions to improve deviceperformance.The major works of this paper are given as follows:Primary，we studied the electronic transport properties of armchair graphene nanoribbon(GNR), and the effects of number of carbon atoms in its transverse direction on effective mass,on-off property, and high frequency property of GNRFETs. The results shows that N=3p (p is aninteger) GNRFETs has high on-state current and high cutoff frequency, and N=3p+1GNRFETs hashigh on-off current ratio.Secondly, we investigated the effect of hetero gate structure and halo doping structure ontransport performance of GNRFETs, and then proposed a new structure-triple-material-gate withhalo doping (TMG-HALO). Though series comparison with triple-material-gate (TMG) GNRFETs,HALO GNRFETs, and traditional GNRFETs, we find that the proposed structure can effectivelysuppress leakage current and short channel effects, enhance carrier Mobility and on-off currentratio(which can reach106), moreover its subthreshold Swing is less than60mV/dec.Thirdly, a new structure, double gate hetero gate dielectric tunnel GNRFETs with linear dopedprofile (SL-HTFETs), is proposed. We present the gate dielectric, linear doped profile variationimpact on drain current, on-off current ratio and high frequency property and short channel effectsof tunnel GNRFETs. Compared with traditional tunnel GNRFETs, the proposed structure cansuppress leakage current, improve on-off current ratio and has better scaling performance.Furthermore, the high frequency performance optimization of the SL-HTFETs is also studied.Finial, Theory of THz radiation and detection for High Electron Mobility Transistor (HEMT)was studied based on Fluid dynamics model. We found that a short channel HEMT has a resonanceresponse to electromagnetic radiation at the plasma oscillatio n frequencies of the two dimensional electrons in the device and this response can be used for detector and mixer. A long channel HEMThas a nonresonant response to electromagnetic radiation and can be used as a broadband detector forfrequencies up to several tens of terahertz.Main conclusions:(1) N=3p (p is an integer) GNRFETs is suitable for application to high-frequency circuits andN=3p+1GNRFETs is application to on-off circuits.(2) Compared with GNRFETs, TMG-HALO structures have better Sub-threshold performance.(3) Compared with tunnel GNRFETs, SL-HTFETs structures have better Sub-thresholdperformance and better scaling performance.(4) GNR is suitable for high-frequency applications...