Modeling And Simulation Of Tunneling Field Effect Transistor

Along with the development of microelectronics technology,traditional integrated circuit technology encountered bottlenecks in miniaturization.Moreover power consumption problem is increasingly serious.The subthreshold swing?SS?of traditional MOSFET cannot achieve lower than 60mV/dec due to the limitation of its working operating.In addition,the reduction of FET's device size is limited by the short channel effect.Recently tunneling field effect transistor?TFET?is considered to be one of the most promising candidates of traditional MOSFET.The channel current in TFET is generated from the electron tunneling between different subbands.As a result SS parameter of TFET can be smaller than 60mv/dec,and the short channel effect is depressed to a certain extent.This thesis is arranged as four parts.In the first part,the differences between TFET and traditional MOSFET are compared from the structure and working operating firstly.Secondly the physical properties of graphene nanoribbon are studied.Because graphene nanoribbon has the advantages of small size,thin thickness,high electron mobility and narrow bandgap,it was proposed as the channel material of device in the this thesis.Finally,the instructions of NanoTCAD software and the rules of grids are introduced.In the second part,a double gate TFET structure is considered,and this classical structure is improved by sandwiching a high doped N region between source and channel,meanwhile the doping concentration is increased as in drain region.The effects of double-gate,length of T region,gate alignment,dielectric constant of gate oxide layer and drain doping concentration on device performance are studied.Compared with the traditional PIN structure,the on state current is greatly improved for the optimized device.And the leakage current and the subthreshold swing is significantly reduced.In the third part,a TFET structure without physical doping is considered.The N type and P type doping are realized by the control of the voltage at multi-gate.Because the heterojunction structure and the physical doping are not adopted in the device,the doping state in the band gap can be avoided as well as the adverse influence of heterojunction boundary state.In this device,the gate-oxide layer is formed by the staggered high-k and losw-k meterial which increases the tunneling probability.Additionally the sizes of L_GAP,SAP,S and L_GAP,DAP,D are optimized in order to gain a high on-off current ratio.The forth part is the summary and prospect of the full text.