Characteristics of polycrystalline-Si thin film transistors fabricated by excimer laser annealing method

The electrical characteristics of excimer laser annealed (ELA) polycrystalline-Si thin film transistors (poly-Si TFT´s) were investigated. These results were compared to those of poly-Si TFT fabricated by solid phase crystallization (SPC). From the temperature dependence of the drain current, the activation energies of n-type poly-Si TFT´s were obtained. The activation energies have negative values under the gate voltage from 0 to 5 V. The negative activation energy together with small threshold voltage (V_th) are the main characteristics of ELA poly-Si TFT. Temperature dependencies of V _th, and field effect mobility are very similar to those of SPC. From these results, it is concluded that the trap state density of ELA poly-Si TFT is very small and the electrical characteristics can be explained by the band tail states localized at the grain boundary