Oxide TFT Stack for Fast UHD Pixel Charging Stability
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Solution Overview
Problem
Ultra-high definition (UHD) flat display devices require high-speed driving, which leads to shortened one-line scanning times, potentially causing image quality deterioration due to insufficient data voltage charging in pixels, necessitating a thin film transistor with high electron mobility and short channel length.
Innovation Solution
A thin film transistor with an oxide semiconductor layer composed of iron-indium-zinc oxide (FIZO) and indium-gallium-zinc oxide (IGZO) is developed, where the FIZO layer has a higher indium content than zinc and iron, and the IGZO layer has a greater zinc-to-indium ratio, with the IGZO layer providing higher resistance and band-gap energy to enhance electron mobility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the one-line scanning time is shortened to achieve high-speed driving in UHD display devices, then the driving speed is improved, but the pixel cannot be charged with desired data voltage leading to image quality deterioration
Solution Approach 1:
The patent changes the material composition parameters of the oxide semiconductor layer by incorporating iron (Fe) along with indium (In) and zinc (Zn), optimizing the atomic ratios to achieve higher electron mobility. This material parameter change enables the transistor to operate at higher speeds while maintaining sufficient charging capability for pixels during shortened scanning periods, thus resolving the contradiction between driving speed and image quality.
Solution Approach 2:
The patent uses a composite oxide semiconductor material system (Fe-In-Zn-O) combining multiple metal oxides. This composite material approach leverages the beneficial properties of each component: indium for high electron mobility, zinc for stability, and iron for enhanced carrier concentration. The composite structure achieves both high-speed operation and reliable pixel charging within shortened scanning times.
2Speed
If the oxide semiconductor layer uses high indium content to increase electron mobility, then the driving speed is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent optimizes the compositional parameters of the oxide semiconductor layer by establishing specific atomic ratio ranges (Fe/In < Zn/In and In > Zn > Fe). These parameter specifications enable high electron mobility through increased indium content while providing clear manufacturing guidelines that reduce complexity. The defined parameter ranges allow for controlled deposition processes and simplify quality control during fabrication.
Data Source
AI summary
Disclosed are a thin film transistor having an oxide semiconductor layer which is applicable to a flat display device requiring high-speed driving due to ultra-high definition, a gate driver including the same, and a display device including the same. The thin film transistor includes a first oxide semiconductor layer formed of iron-indium-zinc oxide (FIZO) and a second oxide semiconductor layer formed of indium-gallium-zinc oxide (IGZO), thus being capable of exhibiting effects, such as high reliability and high electron mobility.