Concave Mesa Edge Structure for LED Light Extraction
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Solution Overview
Problem
Current light-emitting devices face challenges in enhancing light extraction efficiency and production yield, while also ensuring the reliability of the package apparatus.
Innovation Solution
The design includes a substrate with a semiconductor stack featuring a specific pattern on its side surfaces, comprising concave and convex parts, and strategically positioned semiconductor structures to optimize light emission and electrical current distribution, along with an identification pattern for improved cutting process accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat semiconductor mesa structure is used, then the device structure is simple, but the light extraction efficiency is low
Solution Approach 1:
The patent applies curvature by forming a concave portion (hemispherical or dome-shaped) at the top surface of the semiconductor mesa. This curved structure increases the light extraction efficiency by reducing total internal reflection and enabling light to escape more effectively from the high-refractive-index semiconductor material to the lower-refractive-index packaging material.
Solution Approach 2:
The patent introduces a vertical dimension change by creating a concave portion that extends downward from the top surface of the semiconductor mesa. This dimensional change creates multiple light extraction pathways and increases the effective surface area for light emission, thereby improving light extraction efficiency.
2Reliability
If the semiconductor mesa structure is modified to improve light extraction, then the light extraction efficiency increases, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the top surface of the semiconductor mesa into a central concave portion and surrounding flat regions. This segmentation allows the complex light extraction function to be localized in the concave area while maintaining simpler structures in other regions, balancing performance improvement with manufacturing feasibility.
3Volume of moving object
If electrode pads are positioned close to each other, then the device volume is reduced, but the risk of short circuit increases
Solution Approach 1:
The concave portion creates a curved, dome-shaped structure that naturally increases the distance between electrode pads positioned on its surface. This spherical geometry allows electrodes to be placed closer in planar projection while maintaining adequate physical separation through the three-dimensional curvature, reducing short circuit risk without increasing device footprint.
Data Source
AI summary
A light-emitting device includes a substrate including a top surface, a first side surface and a second side surface, wherein the first side surface and the second side surface of the substrate are respectively connected to two opposite sides of the top surface of the substrate; a semiconductor stack formed on the top surface of the substrate, the semiconductor stack including a first semiconductor layer, a second semiconductor layer, and an active layer formed between the first semiconductor layer and the second semiconductor layer; a first electrode pad formed adjacent to a first edge of the light-emitting device; and a second electrode pad formed adjacent to a second edge of the light-emitting device, wherein in a top view of the light-emitting device, the first edge and the second edge are formed on different sides or opposite sides of the light-emitting device, the first semiconductor layer adjacent to the first edge includes a first sidewall directly connected to the first side surface of the substrate, and the first semiconductor layer adjacent to the second edge includes a second sidewall separated from the second side surface of the substrate by a distance.