Simulation Of Electrical Properties Of Ferroelectric Field Effect Transistor With Graphene Channels

Ferroelectric field effect transistor(FeFET) has attracted much attention because of its higher integration, anti-radiation, non-destructive, readout capability. Silicon is most often used for the channels of the FeFET. However, the FeFET with silicon channels has poor retention property because of the serious diffusion in the interface of silicon/ferroelectric. Grapheme is a good replacer for Si when it is used as channels in FeFET. The reasons are following. First, the interface of graphene/ferroelectric is very good with little diffusion. Then, the size of graphene is small, and its mobility is high, which are good for the application in memory with high density and high speed.In this thesis, metal-ferroelectric-graphene namely a MFG-FET capacitor is built and the properties of the MFG-FET are simulated. Especially, the effects of the ferroelectric layers and the substrate materials on the properties of the MFG-FET are studied systematically. The main work and results are given as follow.(1) By considering graphene quantum capacitance effect, a model of the properties of MFG-FET which based on Lue model and graphene quantum transport model is built. The effects of applied voltage on C-V characteristic, memory window of MFG-FET and I-V characteristic are simulated. The simulation results show that the MFG-FET demonstrates a smaller drain current, and wider memory window compared with the FeFET with silicon channels.(2) According to the built model, the effects of the substrate materials on the properties of the MFG-FET are simulated. The simulation results show that the Fermi velocity of the graphene channels layers increases with decreasing the relative dielectric constant of the substrate interface. The low total capacitance of the MFG-FET decreases with increasing the Fermi velocity while the high total capacitance remains the same, so the ratio of high/low total capacitance changes bigger. Meanwhile, the ON current of the MFG-FET decreases with increasing the Fermi velocity.(3) According to the built model, the effects of the ferroelectric layers on the properties of the MFG-FET are simulated. The simulation results show that the memory window of the MFG-FET increases firstly and then decreases with increasing the ferroelectric layers thickness. The power consumption is reduced by increasing the ferroelectric layers. The high-low total capacitance of the MFG-FET increases and thememory window of the MFG-FET decreases with increasing the relative dielectric constant of the ferroelectric layers. The power consumption is reduced by decreasing the relative dielectric constant. The memory window of the MFG-FET decreases with increasing the spontaneous polarization of ferroelectric layers and the memory window of the MFG-FET increases with increasing the residual polarization of ferroelectric layers.