A Compact Model for Undoped Symmetric Double-Gate Polysilicon Thin-Film Transistors

A physics-based solution to the surface potential and potential in the middle of the film for the symmetric undoped or light-doped double-gate (DG) polysilicon thin-film transistors (poly-Si TFTs) has been derived from the one-dimensional (1-D) Poisson´s equation. The calculation of the channel potential accounts for an exponential distribution of defect states´ density. It provides a good description of surface potential over different regions of operation. Comparison with numerical data shows that the solution serves as a good approximation to potential under different conditions. The characteristics of the drain current at DG poly-Si TFTs based on terms of surface potential have been described and modeled in this paper. The resulting drain current characteristics show a good agreement with two-dimensional (2-D) numerical device simulations with a minimum of parameters, and also a good match to the DG poly-Si TFTs experimental data.