The Research Of Compact Models For Single-gate And Surrounding-gate Poly-Si Thin Film Transistors Based On Surface Potential

Polysilicon thin-film transistors,due to theirs great electrical characteristics and low cost of preparation,have been widely used in all kinds of electronic products,which provide convenience for our daily life.Because the electrical characteristics of poly-Si TFT directly affect the performances of electronic products,poly-Si TFT compact model has been in the intensive research to achieve simulating DC and AC properties.However,only a few models of poly-Si TFT have been published in the literatures.Up to now,there is a technical bottleneck remaining in the process of modelling poly-Si TFT.It is describing the effect on the electrical characteristics from the trap states existing in the grain boundaries of polysilicon channel films.Therefore,a compact model of poly-Si TFT with considering the trap states is urgently necessary to represent the performances of poly-Si TFT and aid circuit simulations.This paper focuses on building the AC/DC models of single-and surrounding-gate polysilicon TFTs as follows.On one side,we complete the compact model of single-gate poly-Si TFTs.Firstly,surface potential is solved from the 1-D Poisson Equation.Subsequently,the analytical expression of drain current is derived based on the surface potential.Then,the capacitance model is obtained by using the terminal charge.On the other side,we propose the compact model of surrounding-gate poly-Si TFTs,which have better short channel suppression ability than the single-gate ones.Firstly,surface potential is derived explicitly by introducing the effective charge and the intermediate variable.Secondly,the drain current is integrated analytically from the Pao-Sah equation.Finally,similar as single-gate poly-Si TFT,the gate capacitance model are provided based on the terminal charges.In conclusion,single-and surrounding-gate poly-Si TFT models are proposed in this paper to be implemented into circuit simulators.The established models have the advantages of clear physical meaning and simple algorithm.