Achieving High Performance Oxide TFT-Based Inverters by Use of Dual-Gate Configurations With Floating and Biased Secondary Gates

A dual-gate thin-film transistor (TFT) has two gate electrodes. In inverted, staggered TFTs, the primary gate is usually the bottom gate (BG) and the TFT´s threshold voltage (VTH) can be adjusted by applying a constant bias to the secondary gate, the top gate (TG), while scanning the BG. Dual-gate TFTs are being used as the load TFT in oxide semiconductor-based inverters, where the TG is biased positively to shift the VTH negatively and, thereby improving the inverter´s output swing. Here, we show that the same can be achieved by the use of a floating TG. Furthermore, we show that the noise margin of the inverter can also be controlled by adding a biased TG to the driving TFT.