Micro LED Stack Pillar Layout That Preserves Emitting Area
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Solution Overview
Problem
The challenge in developing micro LEDs for display applications, such as augmented reality, is the reduction in light emitting area due to the use of through vias, which increases non-radiative surface recombination and lowers external quantum efficiency, especially as the size of micro LEDs decreases, making it difficult to reduce via size proportionally due to equipment performance limitations.
Innovation Solution
A stacked light emitting device with a novel electrical connection structure using pillars instead of through vias to connect LED stacks, allowing for independent electrical connection of each LED stack without reducing the light emitting area, thereby reducing non-radiative surface recombination and enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through vias are used to connect LED stacks, then electrical connection is achieved, but light emitting area is reduced and non-radiative surface recombination increases
Solution Approach 1:
The patent transitions from planar via connections to three-dimensional pillar structures that extend vertically along the LED stack. This dimensional change allows electrical connection without penetrating the light emitting region, thus preserving the light emitting area while achieving reliable electrical connectivity through side-surface contact.
Solution Approach 2:
The patent introduces pillar structures as intermediary elements that provide electrical connection between LED stacks without directly interfering with the light emitting region. These pillars act as mediators that conduct electricity while maintaining spatial separation from the active light emitting area, thus resolving the conflict between connection reliability and light emitting area preservation.
2Length of moving object
If micro LED size is reduced to enable smaller displays, then display density increases, but via size reduction is limited by equipment performance
Solution Approach 1:
The patent moves the connection structure from a planar via approach to a vertical pillar configuration. This allows the connection elements to scale with the micro LED size without being constrained by equipment limitations in reducing via dimensions, as the pillars extend in the vertical dimension rather than requiring proportional reduction in lateral dimensions.
Solution Approach 2:
The patent segments the connection function from the light emitting region by using separate pillar structures. This segmentation allows independent optimization of connection reliability and light emitting area, enabling micro LED size reduction without being constrained by via size limitations.
3Area of moving object
If pillar structure is used instead of through vias, then light emitting area is preserved, but electrical connection complexity increases
Solution Approach 1:
The patent designs pillar structures that serve multiple functions: providing electrical connection, maintaining structural integrity, and preserving light emitting area. This multi-functionality reduces the need for separate connection mechanisms, thereby managing complexity while achieving the desired light emitting area preservation.
Solution Approach 2:
The patent merges the electrical connection function with the structural support function into a single pillar structure. This consolidation simplifies the overall device architecture by eliminating the need for separate via structures and reducing the number of manufacturing steps, thus managing complexity while preserving the light emitting area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively alleviates the reduction in light emitting area and prevents current leakage, improving the external quantum efficiency of micro LEDs, enabling their use in smaller sizes like 5 μm×5 μm or less without the performance limitations of conventional via-based structures.
Implementation Method 1
light emitting diodes have been used in various fields including displays
Data Source
AI summary
A light emitting device including an insulation unit, a light emitting region including first, second, and third LED stacks each including first and second conductivity type semiconductor layers, a first pillar electrically connected to the first conductivity type semiconductor layers of the first, second, and third LED stacks, and a second pillar, a third pillar, and a fourth pillar electrically connected to the second conductivity type semiconductor layers of the first, second, and third LED stacks, respectively, an intermediate first connector and a lower first connector respectively electrically connecting the first conductivity type semiconductor layers of the second LED stack and the third LED stack to the first pillar, in which the insulation unit have four corners, and the first, second, third, and fourth pillars are disposed near the four corners covering a side surface of the insulation unit, respectively.