1/f noise characterization of amorphous/nanocrystalline silicon bilayer thin-film transistors

Bottom-gated n-channel thin-film transistors (TFTs) were fabricated on amorphous silicon (a-Si)/nanocrystalline silicon (nc-Si) bilayers, deposited at 230°C by plasma-enhanced chemical vapour deposition. The impact of the channel length on the electrical and low-frequency noise characteristics of the TFTs is investigated. The results show that the 1/f noise can be interpreted in terms of carrier number fluctuations, except the long channel devices where the 1/f noise is interpreted in terms of the Hooge’s mobility fluctuations model at low drain currents. The gate insulator trap density has been evaluated, demonstrating that the nc-Si extended underneath the n+ drain contact area contributes to the measured noise.