Threshold voltage control in dual gate ZnO-based thin-film transistors operating at 5 v

We report on the fabrication of ZnO-based dual gate (DG) thin-film transistors (TFTs) with 20 nm thick Al₂O₃ for both top and bottom dielectrics, which were deposited by atomic layer deposition on glass substrates at 200 °C. Whether the top or the bottom gate is biased for sweep or not, our TFT operates almost symmetrically under a low voltage of 5 V showing a field mobility of ∼0.4 cm² V^-1 s ^-1 along with the on/off ratio of 5 × 10⁴. The threshold voltage of our DG TFT was systematically controlled from 0.5 to 2.0 V by varying the counter gate input from +5 to -2 V.