Current crowding and 1/f noise in polycrystalline silicon thin film transistors

Here we investigate dc characteristics, impedance versus frequency, and low frequency noise. The effect of current distribution on 1/f noise in polycrystalline silicon thin film transistors (TFTs) is discussed. We show that the channel impedance versus frequency roll induces spectra that could be misinterpreted above a corner frequency in terms of a frequency index γ in 1/fγ with γ higher than 2. Moreover, ignoring the inhomogeneous current distribution leads to overestimation of the noise parameter. Whereas it seemed evident that the noise in TFTs can be interpreted in terms of carrier number fluctuation, the noise parameter variation versus the gate bias can be also understood in terms of mobility fluctuations by including the potential barrier evolution.