Analysis of current-voltage characteristics in polysilicon TFTs for LCDs

An analytic model which can accurately calculate the characteristics of polysilicon TFTs was developed. The theoretical current-voltage curves were compared with measured data, and correlations with trap density in polysilicon film and device performance were investigated. Good agreement was obtained between theoretical and measured results. It was also found that on-current was improved by reducing the densities near the band edges in a forbidden gap. This effect was realized by optimizing the film deposition temperature or by using laser annealing. A hydrogenation effect reduced the density near the midgap, which improved off-current. The TFTs were successfully applied in grey-scale liquid-crystal displays (LCDs) with fully integrated drive circuits.<>