Oxide TFT Pixel Circuit with Double-Gate Threshold Control
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Solution Overview
Problem
The use of oxide semiconductors in thin-film transistors for flat panel display devices results in non-uniform threshold voltages, leading to deteriorated image quality and performance due to changes in electrical properties with configuration and processing conditions.
Innovation Solution
A pixel circuit with a double-gate oxide thin-film transistor structure, where the oxide semiconductor, such as ZnO, is doped with ions like Ga, In, Sn, Zr, or V, and threshold voltages are controlled by a voltage level of a controlling signal, maintaining consistent threshold voltages and improving current properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor is used as active layer in thin-film transistor, then manufacturing cost is reduced and low-temperature processing is enabled, but threshold voltage becomes non-uniform and electrical properties deteriorate
Solution Approach 1:
The patent applies parameter changes by doping the oxide semiconductor with various elements (Ga, In, Sn, Zr, V, Al, B, C, Si, Ge, Ni, Pd, Pt, Mo, W) to modify the electrical properties and threshold voltage characteristics. This allows maintaining the low-temperature manufacturing advantage while improving threshold voltage uniformity through controlled compositional changes in the oxide semiconductor layer.
Solution Approach 2:
The patent uses composite materials by creating doped oxide semiconductors where metal elements are incorporated into the oxide semiconductor matrix. This composite structure combines the benefits of oxide semiconductors (low-temperature processing, low cost) with the advantageous electrical properties of the dopant elements, achieving both ease of manufacture and improved reliability.
2Device complexity
If oxide thin-film transistor is used in pixel circuit, then device complexity is reduced, but image quality deteriorates due to non-uniform threshold voltages
Solution Approach 1:
The patent modifies the compositional parameters of the oxide semiconductor by introducing specific metal dopants at controlled concentrations. This changes the electrical characteristics to achieve more uniform threshold voltages across the display, thereby improving image quality while maintaining the simple oxide TFT circuit structure.
Solution Approach 2:
The patent applies local quality by selectively doping different regions or layers of the oxide semiconductor with specific elements to optimize local electrical properties. This ensures uniform threshold voltage characteristics across different areas of the display device, improving overall image quality without increasing device complexity.
Data Source
AI summary
A pixel circuit of a flat panel display device and a method for driving thereof are provided. The pixel circuit includes a first transistor having a first gate electrode coupled to a scan line, a second electrode coupled to a data line, a second gate electrode coupled to a controlling signal line, and a first electrode, a second transistor having a first gate electrode coupled to the first electrode of the first transistor, a second electrode coupled to a first voltage source, a second gate electrode coupled to the controlling signal line, and a first electrode, a capacitor coupled between the first gate electrode of the second transistor and the first electrode of the second transistor, and an organic light emitting diode coupled between the first electrode of the second transistor and a second voltage source, in which the threshold voltage of the first and second transistors may be controlled to the required level by supplying a controlling signal of a fixed voltage level to the second gate electrodes of the first and second transistors through the controlling signal line.