1/f Noise Characterization of n- and p-Type Polycrystalline-Silicon Thin-Film Transistors

This paper presents a study of low-frequency-noise properties of n- and p-type polycrystalline-silicon (poly-Si) thin-film transistors (TFTs). The 1/f noise behavior of these devices prompted the use of the carrier number with correlated mobility fluctuation model for data analysis. From this model, trap densities in this study were found to range from 3.5 x 10(16) to 4 x 10(17) states/eV . cm(3), which is indicative of a good top surface of the channel and interface between the oxide and poly-Si. The normalized current noise of the p-channel TFTs changes with the inverse of current, independent of the width (W)-to-length (L) ratio of the channel; the normalized current noise of the n- channel TFTs also changes with the inverse of current, but not independent of the W/L ratio. For smaller currents, noise is caused by traps at or near the oxide/semiconductor interface, whereas for larger currents, the larger contribution to the noise is believed to originate from the bulk.