A Study on High Performance, Dual-Gate a-IZO/a-IGZTO TFTs With Excellent Stability

We report a high-performance dual-gate, dual-sweep (DS) a-IZO/a-IGZTO TFT with high field-effect mobility (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu _{\text {FE}}\text {)}$ </tex-math></inline-formula> of 65 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V.s, threshold voltage (V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {TH}}\text {)}$ </tex-math></inline-formula> of 0.4V, subthreshold swing (SS) of 0.23 V/dec and high on/off current ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{7}}$ </tex-math></inline-formula>. A systematic study on the bias stress effect has been carried out by making accumulation or depletion at the interface with bottom gate (BG) or top gate (TG) bias. Technology computer-aided design (TCAD) simulation results fitted well with measurement data using the density of states for a-IZO and a-IGZTO. Positive-bias temperature stability tests were conducted at 60°C for 1 hr using a +20V stress voltage, based on the V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub>, showed negligible V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> shift for all bias stress cases. These results suggest that the a-IZO/a-IGZTO TFT, with its high mobility with excellent stability, could be suitable for large area AMOLED displays.