A Surface-Potential-Based Drain Current Compact Model of Dynamic-Depletion Polysilicon Thin-Film Transistors

An analytical surface-potential-based drain current model of dynamic-depletion (DD) polysilicon (poly-Si) thin-film transistors (TFTs) is proposed in this paper. In the 1-D Poisson equation, total charge density is reformulated by an effective charge density, which allows a closed-form surface potential calculation scheme. Different boundary conditions between partial depletion and full depletion are calculated and unified into one back-gate potential in the DD mode, which allows a unified-form surface potential calculation scheme. Combining with Gauss's theory, we explicitly solve a closed- and unified-form surface potential of DD poly-Si TFTs. Based on the solution of the surface potential, the drain current is derived analytically from the Pao-Sah integration. Furthermore, our solution is verified by numerical results and experimental data, respectively. As a result, such a model can accurately predict I-V characteristics of DD poly-Si TFTs and provide computational efficiency for TFT process optimization and circuit simulations.