Mesh-patterned IZO/Hf-doped IGZO thin film transistors with high mobility and mechanical stability for flexible display

Abstract

Despite recent improvements in oxide-based thin-film transistors (TFTs), their performance (i.e., mobility and on/off ratio) must be further enhanced and the fabrication temperature must be decreased to enable the practical use of TFTs in flexible applications. Herein, we introduce mesh-patterned indium-zinc oxide (mIZO)/Hf-doped indium-gallium-zinc oxide (Hf:IGZO) heterojunction TFTs that exhibit superior electrical performance and flexibility without requiring high-temperature annealing during fabrication. Hf, readily bonded to the surrounding ion vacancies, is used in the IGZO channel, thereby decreasing the process temperature. Moreover, a mesh pattern is applied to the channel area, which expands the quasi-two-dimensional electron gas region and increases the number of electrons. Additionally, the mesh pattern reduces the stress experienced by the channel layer, providing superior flexibility with respect to those of planar structures. The proposed mIZO/Hf:IGZO heterojunction TFT exhibits remarkably high mobility (∼40 cm²/Vs) and on/off ratio (∼10⁸) under a low process temperature (150 °C). Furthermore, an organic light-emitting diode driven by the mIZO/Hf:IGZO heterojunction TFT continued operating even after 1000 bending cycles, confirming the superior flexibility of the proposed TFT. This study presents a novel method to achieve superior performance and mechanical flexibility from oxide-based TFTs without high-temperature processes.