Surface Potential-Based Polycrystalline-Silicon Thin-Film Transistors Compact Model by Nonequilibrium Approach

We propose a surface potential-based polycrystalline silicon thin-film transistors (poly-Si TFTs) compact model considering a nonequilibrium state. A drain current model considers grain boundary (GB) trap-related physical phenomena: composite mobility of GB and intragrain, GB bias-induced mobility modulation, transient behavior because of carrier capture and emission at GBs, pinch off voltage lowering, and GB trap-assisted leakage current. Besides, photoinduced current behavior is also considered by introducing quasi-Fermi potential. A capacitance model is derived from physically partitioned terminal charges and coupled to the drain current. This compact model allows us to accurately simulate static characteristics of various types of poly-Si TFTs, including temperature and luminance dependence. Furthermore, it succeeded to simulate frequency dependence of circuit performance derived from the trap-related transient behavior, which was verified by evaluating delay time in a 21-stage inverter chain.