Pixel Driver Circuitry Using Mixed Semiconductor Materials
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Solution Overview
Problem
Current pixel driver circuitry for display devices faces challenges in achieving a balance between high electron mobility for smaller transistors and threshold voltage uniformity, which affects pixel density and power consumption.
Innovation Solution
The use of a combination of semiconductor materials, such as low-temperature polycrystalline silicon (LTPS) and indium gallium zinc oxide (IGZO), where LTPS provides greater electron mobility and stability, and IGZO offers better threshold voltage uniformity, allowing for different channel width-to-length ratios for transistors to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single semiconductor material is used for all transistors in pixel driver circuitry, then manufacturing is simplified, but performance optimization is limited due to inability to balance electron mobility and threshold voltage uniformity
Solution Approach 1:
The pixel driver circuitry is segmented into different transistor types (first transistor, second transistor, third transistor) that use different semiconductor materials. Specifically, the first and second transistors use a first semiconductor material while the third transistor uses a second semiconductor material, allowing each transistor to be optimized for its specific function while maintaining manufacturing feasibility through systematic material assignment.
Solution Approach 2:
Different semiconductor materials are assigned to different transistors based on their specific performance requirements. The first semiconductor material is used for transistors requiring high electron mobility, while the second semiconductor material is used for transistors requiring good threshold voltage uniformity. This local optimization allows each transistor to have the material properties best suited for its function.
2Productivity
If transistors are dimensioned smaller to increase pixel density, then pixel density improves, but threshold voltage uniformity deteriorates
Solution Approach 1:
The invention changes the semiconductor material parameter for specific transistors to address threshold voltage uniformity issues. By using a second semiconductor material for the third transistor that has superior threshold voltage uniformity characteristics, the circuit can achieve reliable performance even with smaller transistor dimensions required for high pixel density displays.
3Speed
If high electron mobility semiconductor material is used, then transistor size can be reduced for higher pixel density, but threshold voltage uniformity becomes problematic
Solution Approach 1:
The pixel driver circuitry employs a composite material strategy where different semiconductor materials are used for different transistors. The first semiconductor material provides high electron mobility for the first and second transistors, while the second semiconductor material provides good threshold voltage uniformity for the third transistor. This composite approach allows the system to achieve both high speed performance and reliable threshold voltage characteristics.
Data Source
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AI summary
A display device comprises a first LED coupled with an input node, and further comprises pixel driver circuitry. The pixel driver circuitry comprises a data input transistor configured to conduct, based on a first control signal, a data signal across a first channel having a first channel W/L ratio. The pixel driver circuitry further comprises a drive transistor configured to conduct, based on the data signal, current across a second channel into the input node. The second channel has a second channel W/L ratio. The pixel driver circuitry further comprises a reset transistor configured to conduct, based on a received second control signal, a first reference voltage signal across a third channel into the input node. The third channel has a third channel W/L ratio. At least one of the first channel W/L ratio, the second channel W/L ratio, and the third channel W/L ratio is different.