Enhanced Interfacial Integrity of Amorphous Oxide Thin-Film Transistors by Elemental Diffusion of Ternary Oxide Semiconductors.

Low-temperature solution-processed oxide semiconductor and dielectric films typically possess a substantial number of defects and impurities due to incomplete metal-oxygen bond formation, causing poor electrical performance and stability. Here, we exploit a facile route to improve the film quality and the interfacial property of low-temperature solution-processed oxide thin films via elemental diffusion between metallic ion-doped InO (M:InO) ternary oxide semiconductor and AlO gate dielectric layers. Particularly, it was revealed that metallic dopants such as magnesium (Mg) and hafnium (Hf) having a small ionic radius, a high Gibbs energy of oxidation, and bonding dissociation energy could successfully diffuse into the low-quality AlO gate dielectric layer and effectively reduce the structural defects and residual impurities present in the bulk and at the semiconductor/dielectric interface. Through an extensive investigation on the compositional, structural, and electrical properties of M:InO/AlO thin-film transistors (TFTs), we provide direct evidences of elemental diffusion occurred between M:InO and AlO layers as well as its contribution to the electrical performance and operational stability. Using the elemental diffusion process, we demonstrate solution-processed Hf:InO TFTs using a low-temperature (180 °C) AlO gate dielectric having a field-effect mobility of 2.83 cm V·s and improved bias stability. Based on these results, it is concluded that the elemental diffusion between oxide semiconductor and gate dielectric layers can play a crucial role in realizing oxide TFTs with enhanced structural and interfacial integrity.