LED Substrate Protrusions and Angled Sidewalls for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) suffer from low light-extraction efficiency due to total internal reflection of light within the semiconductor layers and substrate, which reduces brightness and overall performance.
Innovation Solution
The light-emitting device incorporates a substrate with protrusions made of different materials than the base, and a semiconductor stack with an obtuse angle between its side wall and the main surface, enhancing light extraction by refracting and reflecting light away from the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional flat substrate structure is used, then manufacturing is simple, but light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The substrate surface is segmented into multiple protrusions with different materials and refractive indices, creating a non-uniform surface structure that breaks total internal reflection and improves light extraction efficiency while maintaining manufacturing feasibility through standardized protrusion patterns
Solution Approach 2:
Different regions of the substrate surface are given different local properties through protrusions made of different materials (e.g., SiO2, Si3N4) with varying refractive indices, allowing optimized light extraction in specific areas while maintaining overall structural integrity and manufacturing simplicity
2Illumination intensity
If light is generated in the active layer, then light emission occurs, but light undergoes total internal reflection and cannot be extracted effectively
Solution Approach 1:
The patent converts the harmful effect of total internal reflection into a beneficial one by using protrusions with different refractive indices to refract and reflect light in controlled directions, transforming trapped light into extractable light that improves overall light extraction efficiency
Solution Approach 2:
The protrusions on the substrate surface introduce curved interfaces that alter light propagation paths through refraction and reflection, enabling light to escape the semiconductor layers more effectively by changing its direction away from the total internal reflection condition
3Ease of manufacture
If semiconductor stack with right angle side wall is used, then manufacturing is straightforward, but light divergence angle is large and forward brightness is reduced
Solution Approach 1:
The semiconductor stack side wall is designed with an asymmetric obtuse angle rather than a symmetric right angle, creating an asymmetric light emission pattern that concentrates light in the forward direction while maintaining feasible manufacturing processes through controlled epitaxial growth angles
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 design improves light extraction efficiency, reduces the divergence angle of emitted light, and increases brightness in the forward direction, leading to enhanced optical output power and improved epitaxial quality.
Implementation Method 1
the protrusion and the base include different materials... enhancing light extraction by refracting and reflecting light away from the substrate
Implementation Method 2
enhancing light extraction by refracting and reflecting light away from the substrate
Data Source
AI summary
A light-emitting package, includes: a housing including an opening; a lead frame covered by the housing; a light-emitting device, mounted in the opening and electrically connected to the lead frame, the light-emitting device including: a substrate including: a base with a main surface; and a plurality of protrusions on the main surface, wherein the protrusion and the base include different materials; a semiconductor stack on the main surface, the semiconductor stack including a side wall, and wherein an included angle between the side wall and the main surface is an obtuse angle; wherein the main surface includes a peripheral area not covered by the semiconductor stack, and the peripheral area is devoid of the protrusion formed thereon; and a filling material filling in the opening and covering the light-emitting device.