Voltage characteristics of polysilicon thin films transistors (Poly-Si TFTs)
are related to basic material and device parameters. Understanding and
modeling the electrical behavior of poly-Si TFT require knowledge of
equivalent properties of polysilicon which are strongly affected by defects
present in this material.
A numerical analysis, which studies the electrical characteristics of
small-grains poly-Si TFTs, has been investigated. The density of states
(DOS) in the band gap is modeled by assuming an exponential distribution of
deep and tail states. The proposed model evaluates the influence of both
deep and tail states on the electrical conduction process and the dominant
contribution of tail states on the threshold voltage values while the deep
states in the middle of polysilicon gap controls the lower threshold regime.
The surface potential and ON/OFF current ratio are also calculated. The
comparison of the generated current-voltage characteristics obtained from
numerical simulation TCAD-ATLAS with those reported in the literature show a
good agreement.