Characterization of Low-Frequency Noise in Polycrystalline Silicon Thin-Film Transistors Under Hot-Carrier Stress

This work systematically investigates the low-frequency noise (LFN) characteristics of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) under hot-carrier (HC) stress. Notably, after a certain duration of HC stress, an anomalous increase in the normalized noise power spectral density with increasing overdrive voltage is observed for the first time, which challenges the predictions of conventional LFN models. Model fitting and activation energy analyses indicate that the LFN originates from grain boundaries (GBs) and is attributed to a pinning effect caused by increased GB defect density. Furthermore, as HC stress continues, the accumulation of interface state defects leads to a shift in the dominant LFN mechanism from bulk carrier mobility fluctuation to carrier number fluctuation. These findings provide new insights into the degradation physics of poly-Si TFTs and offer guidance for improving device reliability in practical applications.