Saturation\nMobility of 100 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> in ZnO Thin-Film Transistors through Quantum\nConfinement by a Nanoscale In<sub>2</sub>O<sub>3</sub> Interlayer\nUsin

In\nthis study, we present a comprehensive study on the fabrication\nand characterization of heterojunction In<sub>2</sub>O<sub>3</sub>/ZnO thin-film transistors (TFTs) aimed at exploiting the quantum\nconfinement effect to enhance device performance. By systematically\noptimizing the thickness of the crystalline In<sub>2</sub>O<sub>3</sub> (c-In<sub>2</sub>O<sub>3</sub>) layer to create a narrow quantum\nwell, we observed a significant increase in saturation mobility (μ<sub>SAT</sub>) from 12.76 to 97.37 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. This enhancement, attributed to quantum confinement,\nwas achieved through the deposition of a 3 nm c-In<sub>2</sub>O<sub>3</sub> semiconductor via spray pyrolysis. Various In<sub>2</sub>O<sub>3</sub> layer thicknesses (2–5 nm) were obtained by\nadjusting precursor solution concentration, flow rate, and number\nof spray cycles. Post annealing treatments were employed to reduce\nthe defects at the interface and within the oxide film, enhancing\ndevice stability and performance. Transmission electron microscopy\n(TEM) confirmed the uniformity of the c-In<sub>2</sub>O<sub>3</sub> film thickness, while variations in thickness significantly influenced\nTFT performance, particularly the turn-on voltage (<i>V</i><sub>GS</sub>) due to changes in the carrier concentration. Ultraviolet\nphotoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy\n(XPS) supported the formation of a potential well with a two-dimensional\nelectron gas (2DEG). The study of single and multiple superlattice\nstructures of consecutive c-In<sub>2</sub>O<sub>3</sub> and c-ZnO\nlayers provided insights into the effects of multiple quantum wells\non the TFT performance. This research presents an advanced approach\nto TFT optimization, highlighting high reliability, and environmental\nand bias stabilities. These lead to enhanced mobility and performance\nuniformity through the precise control of c-In<sub>2</sub>O<sub>3</sub> layer thickness for the quantum confinement effect.