A turn-on DC surface-potential-based drain current model for fully-depleted poly-Si thin film transistors

A turn-on DC surface-potential-based drain current model for fully-depleted polycrystalline silicon thin fdm transistors is developed based on the charge sheet model considering both deep and tail acceptor trap states in the grain boundary and the effect of the back surface potential. By integrating the electron concentration, vertically to the polycrystalline silicon/oxide interface, along the inversion layer and using the average electric filed concept, the areal density of the inversion charge with the channel potential is deduced to calculate both the diffusion and the drift components. For the purpose of simplifying the process of the solution, the trapezoidal rule is used to avoid numerical integration in the drift current calculation. In order to further improve the calculation precision in the region where the whole channel is not completely strong inverted, the triangular method is adopted under certain mathematical constraints to replace the usage of the trapezoidal rule in the drift current calculation. Under different state densities, this proposed surface-potential-based drain current model is verified by 2D-device simulation in devices' transfer characteristics under various drain biases.