Light Emitting Structure With Roughened Extraction and Flat Bonding
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Solution Overview
Problem
The roughening of the light extracting surface in semiconductor light emitting devices to enhance light extraction efficiency leads to difficulties in bonding with optical members, resulting in partial or total reflection due to voids and refractive index differences, which reduces the overall light extracting efficiency.
Innovation Solution
A light emitting device configuration where a first light transmissive layer is applied on the roughened light extracting surface of the semiconductor light emitting element, with both the light emitting element and the light transmissive layer having roughened bonding surfaces, and the light transmissive layer and optical member having flat bonding surfaces, allowing for direct bonding without an adhesive, thereby minimizing refractive index differences and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the light extracting surface of the first conductive type layer is roughened to suppress total reflection and enhance light extracting efficiency, then light extracting efficiency is improved, but bonding with optical members becomes difficult and voids are generated at boundary faces
Solution Approach 1:
The invention divides the light extracting surface into two distinct regions: a roughened region for enhanced light extraction and a flat region for optical member bonding. This segmentation allows each region to fulfill its specific function without compromising the other, resolving the contradiction between light extraction efficiency and bonding ease.
Solution Approach 2:
The invention applies different surface qualities to different areas of the light extracting surface. The roughened region provides high light extraction efficiency through suppressed total reflection, while the flat region provides optimal bonding surface quality. This local differentiation of surface properties resolves the contradiction between the two competing requirements.
2Loss of energy
If the light extracting surface is roughened to enhance light extracting efficiency, then light extraction is improved, but voids are generated at boundary faces causing partial or total reflection due to refractive index differences
Solution Approach 1:
The invention segments the light extracting surface into roughened and flat regions, ensuring that the flat bonding region eliminates void formation at boundaries while the roughened region maintains high light extraction efficiency. This spatial separation prevents the harmful total reflection at boundaries while preserving the beneficial light extraction enhancement.
Solution Approach 2:
The invention applies local quality differentiation by creating a flat surface region specifically at the bonding area to eliminate voids and refractive index mismatch issues, while maintaining the roughened surface in the light extraction region. This localized approach resolves the contradiction between light extraction efficiency and boundary reflection prevention.
3Ease of manufacture
If an adhesive agent is used to connect the first conductive type layer and the optical member to avoid voids, then bonding is achieved, but total reflection is likely to be generated at each boundary face due to different refractive indexes
Solution Approach 1:
The invention segments the device structure into distinct regions with specific functions: the roughened light extracting region for high efficiency light extraction and the flat bonding region for optimal optical member connection. This segmentation allows direct bonding without adhesive agents, eliminating the refractive index mismatch problem that would cause total reflection at adhesive boundaries.
Solution Approach 2:
The invention applies local quality optimization by creating a flat surface region at the bonding interface that enables direct bonding between the semiconductor layer and optical member. This local flat region eliminates the need for adhesive agents and prevents total reflection at boundaries, while the roughened region maintains high light extraction efficiency.
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 extracting efficiency by reducing total reflection and maintaining high bonding strength, improving product quality and reliability, and allowing for increased light propagation without absorption by electrodes.
Implementation Method 1
bonding surfaces of the semiconductor light emitting element and the first light transmissive layer are roughened surfaces
Implementation Method 2
a void (that is, a layer of air having a low refractive index) is generated at boundary faces between them because the surface of the first conductive type layer is roughened. If the void exists, a partial or total reflection of the light (hereinafter, simply called 'total reflection') is caused by the Fresnel reflection due to difference in a refractive index between the first conductive type layer and air
Implementation Method 3
a first light transmissive layer, bonding surfaces of the first light transmissive layer and the optical member are flat, and the first light transmissive layer and the optical member are directly bonded
Data Source
AI summary
A method for manufacturing a light emitting device includes: roughening a light extracting surface of a semiconductor light emitting element, forming a first light transmissive layer on an entirety of the roughened light extracting surface, flattening a surface of a first light transmissive layer that is on a side opposite the semiconductor light emitting element, forming a second light transmissive layer on an entirety of a surface of an optical member, flattening a surface of the second light transmissive layer that is on a side opposite the optical member, and directly bonding the flattened surface of the first light transmissive layer and the flattened surface of second transmissive layer by performing surface-activated bonding, atomic diffusion bonding, or hydroxyl bonding.