Light-Emitting Element Electrode Layout for Uniform End Roughness
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Solution Overview
Problem
Existing light-emitting elements often have uneven surface roughness at their end portions, leading to non-uniform characteristics and reduced efficiency in light emission.
Innovation Solution
A light-emitting element with ohmic electrodes at both end portions, where one surface exposed from the electrodes has constant surface roughness, ensuring uniform characteristics. The element includes a light-emitting stack with a first and second semiconductor layer, an active layer, and electrodes, surrounded by an insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional light-emitting elements are manufactured, then production efficiency is maintained, but surface roughness at end portions becomes uneven leading to non-uniform characteristics
Solution Approach 1:
The patent applies preliminary action by forming a mask pattern before etching the light-emitting stack. The mask pattern is designed with specific geometry (wider at top, narrower at bottom) to pre-compensate for the uneven surface roughness that would otherwise occur at end portions. This preliminary structural preparation ensures that when etching occurs, the final exposed surfaces have uniform roughness characteristics, solving the contradiction between manufacturing precision and productivity.
Solution Approach 2:
The patent implements local quality by creating different mask pattern geometries at different locations. The mask pattern has a first width at the top and a second width at the bottom, with the first width being greater than the second width. This localized variation in mask geometry ensures that each end portion of the light-emitting element receives tailored etching treatment, resulting in uniform surface roughness at both end portions while maintaining overall production efficiency.
2Ease of manufacture
If end portions are exposed without uniform surface roughness, then manufacturing process is simple, but contact reliability deteriorates due to non-uniform characteristics
Solution Approach 1:
The patent applies local quality by designing a mask pattern with non-uniform geometry where the first width (top) is greater than the second width (bottom). This localized differentiation in the mask structure ensures that etching produces uniform surface roughness at both end portions of the light-emitting stack. The approach maintains manufacturing simplicity while achieving the reliability needed for good contact characteristics at both ends.
3Manufacturing precision
If asymmetric mask pattern is used to achieve uniform surface roughness, then surface uniformity is improved, but device complexity increases
Solution Approach 1:
The patent implements local quality through an asymmetric mask pattern where the first width is greater than the second width. This localized geometric variation is the minimal complexity needed to achieve uniform surface roughness at both end portions. The mask pattern's asymmetric design is straightforward to manufacture and apply, providing the precision benefit without excessive device complexity.
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
The solution achieves uniform light emission and improved luminous efficiency by ensuring constant surface roughness at the end portions, reducing contact defects and enhancing contact reliability.
Implementation Method 1
removing the first substrate using a laser lift-off method to expose the first electrode
Data Source
AI summary
A light-emitting element includes a first end portion and a second end portion disposed in a length direction of the light-emitting element, a first electrode corresponding to the first end portion, a first semiconductor layer on the first electrode, an active layer on the first semiconductor layer, a second semiconductor layer on the active layer, and a second electrode on the second semiconductor layer and corresponding to the second end portion. The second electrode includes a first layer on the first semiconductor layer, and a second layer on the first layer. The first semiconductor layer includes a p-type semiconductor layer doped with a p-type dopant. The second semiconductor layer includes an n-type semiconductor layer doped with an n-type dopant. The first electrode is in ohmic contact with the first semiconductor layer. The second electrode is in ohmic contact with the second semiconductor layer.