Low frequency noise in long channel amorphous In-Ga-Zn-O thin film transistors

We investigated the low-frequency noise properties in the inverted-staggered amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with the silicon dioxide (SiO2) gate dielectric. The dependence of noise level on gate area indicates that the 1/f noise is the dominate source and the contribution from TFT parasitic resistances can be ignored in long channel devices. The gate voltage dependent noise data closely follow the mobility fluctuation (Delta mu) model, and the Hooge's parameter (alpha(H)) was extracted to be similar to 1.52x10(-3), which is much lower than the reported alpha(H) for a-Si:H TFTs. Finally, in the comparative study, the noise level in an unannealed a-IGZO TFT was found to be higher than that in an annealed device. The present results suggest that the 1/f noise in our a-IGZO TFT samples is sensitive to the active layer quality (i.e., concentration of conduction band-tail and/or deep gap states). In addition, the observed low noise in a-IGZO TFT can be associated with the s-orbital conduction in amorphous oxide semiconductor. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490193]