Low-frequency noise in InSnZnO thin film transistors with high-quality SiO2 gate oxide stacks

Low-frequency noise (LFN) in InSnZnO (ITZO) thin-film-transistors (TFT) with high-quality SiO2 gate oxide (GO) stacks is studied. This stack is fabricated by the plasma enhanced chemical vapor deposition (PECVD) and comprises two single layers. One layer is deposited by a SiH4 source (SiH4–SiO2), and the other uses a tetraethyl-orthosilicate precursor (TEOS-SiO2). The drain current noise power spectral densities follow the typical 1/f rule, and the main origin of LFN changes with the variation of drain current intensities. At low drain current intensities, LFN is affected by grain boundaries in the channel. As the drain current intensities increase, LFN originates from the carrier number fluctuations in devices with single TEOS-SiO2 GOs and from the carrier number with correlated mobility fluctuations in devices with SiO2 stacks GOs. At extremely high drain current intensities, the contact noise acts as a significant source of LFN in devices with SiO2 GO stacks. According to the carrier number with correlated mobility fluctuation (ΔN−Δμ) model, the devices with optimal stacks GOs exhibit a relatively low trap density near the ITZO/SiO2 interface. Additionally, these devices have a lower border trap density in GOs compared to those with single compositions. It demonstrates that high-quality SiO2 stacks reduce traps near the SiO2/ITZO interface, leading to enhanced devices performance. This work provides a precise and efficient method to evaluate the quality of GOs in metal oxide TFTs.