Subthreshold characteristics of polysilicon TFTs

A new analytical polysilicon thin film transistors (poly-Si TFTs) subthreshold current model is presented in this paper. The model is based on the surface potential in subthreshold regime. When assuming an exponential distribution of defect states density, surface potential calculation is derived by using the Lambert W function, which benefits from computational efficiency and is suitable for implementation in circuit simulation. In order to model the subthreshold characteristics, we have calculated the drain current and subthreshold swing. The subthreshold variation with temperature and kink effect is studied. The off-current around flat-band voltage is also calculated. The results are compared with the available experimental data and an excellent agreement has been obtained.