Micro-LED Mesa Wiring Layout for Low-Resistance Light Extraction
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Solution Overview
Problem
Existing micro light-emitting display elements face issues with light source quality due to the placement of cathode electrodes and the risk of warping when using high reflectivity materials to improve light extraction efficiency.
Innovation Solution
The configuration includes a pixel region with light-emitting elements and a connection region outside the pixel area, featuring a semiconductor layer with mesa shapes and a wiring line layer that reduces resistance and improves light source quality, while avoiding complete filling of spaces between mesa structures to prevent warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode electrode is disposed outside the array, then light source quality is improved, but resistance of the common cathode structure increases
Solution Approach 1:
The patent divides the cathode structure into multiple separate cathode electrodes, each corresponding to a specific light-emitting element or group of elements. This segmentation allows each cathode electrode to be independently optimized for low resistance while maintaining the benefit of external placement for improved light source quality. The segmented structure reduces the overall resistance by providing multiple parallel current paths.
Solution Approach 2:
The patent transitions from a planar two-dimensional electrode layout to a three-dimensional structure by adding vertical connections and utilizing multiple layers. The cathode electrodes are positioned outside the pixel array in the horizontal dimension while maintaining electrical connection through vertical conductive paths, effectively using the third dimension to resolve the resistance issue while preserving the light quality improvement.
2Illumination intensity
If spaces between mesas are filled with high reflectivity material, then light extraction efficiency is improved, but warping of the light-emitting element occurs
Solution Approach 1:
Instead of uniformly filling all spaces between mesas with high reflectivity material, the patent applies reflective properties locally at specific critical locations. The wiring line layer is strategically positioned to provide reflection where most beneficial for light extraction, while avoiding excessive material deposition that would cause warping. This localized approach maintains light extraction efficiency while preserving structural stability.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the wiring line layer material and its deposition characteristics. By controlling the thickness, composition, and deposition conditions of the wiring line layer, the patent achieves the desired reflectivity for improved light extraction while maintaining mechanical compatibility with the surrounding structures to prevent warping.
3Reliability
If the wiring line layer is made thicker, then conductivity is improved, but warping risk increases
Solution Approach 1:
The patent optimizes the thickness parameter of the wiring line layer to achieve the optimal balance between conductivity and structural stability. By precisely controlling the thickness within a specific range, the patent ensures sufficient electrical conductivity for reliable operation while maintaining mechanical compatibility with the mesa structures to avoid warping. This parameter optimization represents a careful trade-off between electrical and mechanical requirements.
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 configuration enhances light source quality and reduces resistance, preventing warping and simplifying the manufacturing process by maintaining the wiring line layer's position below the mesa surface.
Implementation Method 1
a wiring line layer forming a conductive path between the second conductive layers of the plurality of mesa shapes
Implementation Method 2
a plurality of mesa shapes formed by dividing the semiconductor layer into portions corresponding to each of the plurality of light-emitting elements
Implementation Method 3
a step portion separated from the plurality of mesa shapes by a groove formed in the semiconductor layer in the connection region
Data Source
AI summary
An image display element, provided with a pixel region and a connection region, includes a light-emitting unit and a driving circuit substrate. The light-emitting unit includes a semiconductor layer obtained by layering a second conductive layer, a light-emitting layer, and a first conductive layer, mesa shapes formed by dividing the semiconductor layer, and a step portion separated from the mesa shapes by a groove. A first electrode is connected to the first conductive layer and a first driving electrode. The light-emitting unit further includes, between the mesa shapes adjacent to each other, a wiring line layer forming a conductive path, the wiring line layer being thinner than a layer thickness of a portion of each of the mesa shapes in the semiconductor layer. The wiring line layer extends to a top of the step portion and is connected to a common second electrode provided on the step portion.