Modeling kink effect in the poly-Si TFTs under charge sheet approach

In this paper we use a charge sheet approach in post saturation which studies the excess current resulting from the impact ionization occurring at high drain biases of the polysilicon thin film transistor (poly-Si TFT). The proposed model evaluates the increase in the inversion layer charge density caused by the high electric field in the pinch-off region near the drain which leads to the kink effect. The charge sheet model is thus a precise evaluation to describe the output characteristics of n-channel poly-Si TFT. Comparison between the model and others results show an excellent agreement taking into account different geometrical and structural parameters such as channel lengths, widths and various grains sizes of polysilicon layer.