Pixel Circuit Gate Insulator Layout for Leakage and Driving Range
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Solution Overview
Problem
Existing display devices face challenges in achieving stable color expression due to high leakage currents in switching transistors and limited driving range of driving transistors, which are not adequately addressed by adjusting the thickness or material of the gate insulating layer in existing OLED displays.
Innovation Solution
A multi-layer gate insulating structure is implemented, comprising silicon oxide, silicon nitride, and optionally silicon oxynitride layers, with varying thicknesses and hydrogen concentrations to optimize the equivalent oxide thickness and hydrogen concentration across different regions of the active layer, thereby reducing leakage currents in switching transistors and enhancing the driving range of driving transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform gate insulating layer is used across all transistor regions, then the manufacturing process is simple, but the leakage current of switching transistors cannot be sufficiently reduced and the driving range of driving transistors is limited
Solution Approach 1:
The gate insulating layer is designed with different thicknesses in different regions: a first thickness in the switching transistor region and a second thickness in the driving transistor region. This local differentiation allows the switching transistor to have reduced leakage current due to the thinner gate insulating layer, while the driving transistor maintains a larger driving range due to the thicker gate insulating layer, thereby resolving the technical contradiction between reducing leakage current and maintaining driving range.
2Reliability
If the gate insulating layer thickness is increased to reduce leakage current, then switching transistor performance improves, but the driving range of the driving transistor decreases
Solution Approach 1:
The gate insulating layer is designed with different thicknesses in different regions: a first thickness in the switching transistor region and a second thickness in the driving transistor region. This local differentiation allows the switching transistor to have reduced leakage current due to the thinner gate insulating layer, while the driving transistor maintains a larger driving range due to the thicker gate insulating layer, thereby resolving the technical contradiction between reducing leakage current and maintaining driving range.
3Reliability
If hydrogen concentration is increased in the active layer, then leakage current decreases, but the driving range and color expression capability are limited
Solution Approach 1:
The active layer is designed with different hydrogen concentrations in different regions: a first hydrogen concentration in the switching transistor region and a second hydrogen concentration in the driving transistor region. This local differentiation allows the switching transistor to have reduced leakage current due to the higher hydrogen concentration, while the driving transistor maintains a larger driving range due to the lower hydrogen concentration, thereby resolving the technical contradiction between reducing leakage current and maintaining driving range.
Data Source
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AI summary
A display device includes: a substrate; and a plurality of pixel circuits on the substrate comprising: an active layer including a first region and a second region; a gate insulating layer on the active layer, the gate insulating layer including a first insulating layer overlapping the first region and the second region, a second insulating layer on the first insulating layer and overlapping the first region, and a third insulating layer on the second insulating layer and overlapping the first region and the second region; and a first conductive layer on the gate insulating layer, the first conductive layer including a first gate electrode overlapping the first region to form a driving transistor, and a second gate electrode overlapping the second region to form a switching transistor.