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In this work, we systematically investigated the carrier transport of hysteresis-free amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) incorporating high- k (HfO2) x (Al2O3) y gate dielectrics with different composition and permittivity by atomic layer deposition. A dielectric surface morphology dominated interface scattering carrier transport mechanism is demonstrated, and the effect of the dielectric polarization and the interface states on the carrier mobility is discovered in TFT devices gated by high quality dielectrics with negligible charge trap effect. Accordingly, an a-IGZO TFT gated by (HfO2)0.5(Al2O3)0.5 dielectric with the smoothest surface exhibits the best performance in terms of a preferable field-effect mobility of 18.35 cm2 Vâˆ'1 sâˆ'1, a small subthreshold swing of 0.105 V decadeâˆ'1, a high on/off current ratio of 4.6 Ă— 106, and excellent stability under positive bias stress. [ABSTRACT FROM AUTHOR]

Solution deposition of high-quality dielectric films is one of the big challenges in achieving excellent electrical performance of bi-layer solution-processed metal oxide (MO) thin film transistors (TFTs). Using an oxygen-doped precursor solution (ODS), we successfully deposited high-quality zirconium oxide (ZrO2) dielectric films by a solution process. The ODS-ZrO2 films show low leakage current density (10−7 A cm−2 at 2 MV cm−1), high breakdown electric field (7.0 MV cm−1) and high permittivity (19.5). Consequently, solution-processed indium oxide (In2O3) TFTs with ODS-ZrO2 film as the gate dielectric show excellent electrical performance, for example high carrier mobility up to 62.02 cm2 V s−1, a large on/off drain current ratio of 3.0 × 106, a small subthreshold swing of 0.14 V and excellent bias stress stability. Our work demonstrates the critical role of the dielectric film in the electrical performance of MO-TFTs. More importantly, we reveal that high dielectric constant (κ) dielectric film deposited with ODS should be an effective way to significantly increase the electrical properties of MO-TFTs for future low-cost, high-performance applications. [ABSTRACT FROM AUTHOR]