| Summary: | Herein, we investigated the effects of active layer thickness (<i>t<sub>S</sub></i>) on the electrical characteristics and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). IGTO TFTs, with <i>t<sub>S</sub></i> values of 7 nm, 15 nm, 25 nm, 35 nm, and 50 nm, were prepared for this analysis. The drain current was only slightly modulated by the gate-to-source voltage, in the case of the IGTO TFT with <i>t<sub>S</sub></i> = 50 nm. Under positive bias stress (PBS), the electrical stability of the IGTO TFTs with a <i>t<sub>S</sub></i> less than 35 nm improved as the <i>t<sub>S</sub></i> increased. However, the negative bias illumination stress (NBIS) stability of these IGTO TFTs deteriorated as the <i>t<sub>S</sub></i> increased. To explain these phenomena, we compared the O1s spectra of IGTO thin films with different <i>t<sub>S</sub></i> values, acquired using X-ray photoelectron spectroscopy. The characterization results revealed that the better PBS stability, and the low NBIS stability, of the IGTO TFTs with thicker active layers were mainly due to a decrease in the number of hydroxyl groups and an increase in the number of oxygen vacancies in the IGTO thin films with an increase in <i>t<sub>S</sub></i>, respectively. Among the IGTO TFTs with different <i>t<sub>S</sub></i>, the IGTO TFT with a 15-nm thick active layer exhibited the best electrical characteristics with a field-effect mobility (<i>µ</i><sub>FE</sub>) of 26.5 cm<sup>2</sup>/V·s, a subthreshold swing (SS) of 0.16 V/dec, and a threshold voltage (V<sub>TH</sub>) of 0.3 V. Moreover, the device exhibited robust stability under PBS (ΔV<sub>TH</sub> = 0.9 V) and NBIS (ΔV<sub>TH</sub> = −1.87 V).
|
|---|
