Turn-on characteristics of polycrystalline silicon TFT´s-impact of hydrogenation and channel length

Experimental measurements and two-dimensional (2-D) numerical simulation have been used to investigate the impart of the polycrystalline silicon (poly-Si) density of states (DOS) and channel dimensions on the transient response of poly-Si thin-film transistors (TFTs). TFTs exposed to different hydrogenation times were used to investigate the effect of the poly-Si DOS. The experimental results show that TFT turn-on time increases with increasing channel length and decreases with increasing hydrogenation time. For the first time, transient simulations were carried out using "best fit" poly-Si DOS distributions which were extracted numerically from DC transfer characteristics. The resulting simulations show excellent agreement with the experimental data. Degradation in the transient characteristic is thereby correlated with an increase In the poly-Si DOS.