Group-III Nitride LED with Concave Substrate for Light Extraction
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Solution Overview
Problem
Conventional semiconductor light emitting elements face challenges in achieving sufficient light extraction efficiency due to total internal reflection of light at the interface between the semiconductor layer and the surrounding medium, limiting the amount of light that can be extracted from the on-axis direction.
Innovation Solution
A group-III nitride compound semiconductor light emitting element is designed with a substrate featuring concave and convex portions, forming clearances and voids between the substrate and the semiconductor layer, which enhances light extraction efficiency by total reflection of light at the interface with air or resin, allowing more light to be extracted from the on-axis direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light is directed from the semiconductor layer to the outside, then light extraction is possible, but total internal reflection occurs at the interface for light at or above the critical angle, limiting extraction efficiency
Solution Approach 1:
The substrate surface is divided into multiple concave portions with different orientations. Each concave portion has side surfaces that are inclined at different angles relative to the normal of the substrate main surface, allowing light to be extracted through multiple different paths and angles, thereby reducing the impact of total internal reflection
Solution Approach 2:
Different regions of the substrate surface have different local geometries (concave portions with varying inclinations). This local variation in surface quality allows light to be extracted more efficiently from different locations, with each local region optimized for specific light extraction angles
2Illumination intensity
If the side surface angle of the semiconductor layer is changed to increase light extraction, then more light can be transmitted to the outside, but the effect is limited because light propagation to the side surface is restricted
Solution Approach 1:
The invention introduces vertical dimensionality by creating concave portions that extend downward from the substrate surface. This allows light to be extracted not only from the top surface but also from the side surfaces of the concave portions, effectively adding another dimension for light extraction pathways
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 design significantly improves light extraction efficiency by reflecting light at the interface between the semiconductor layer and the surrounding medium, resulting in increased brightness and improved light transmission from the semiconductor light emitting device.
Implementation Method 1
the light directed toward the substrate from the group-III nitride compound semiconductor layer is almost totally reflected at the interface between the semiconductor layer and an air layer (or resin layer region
Data Source
AI summary
A group-III nitride compound semiconductor light emitting element includes a substrate that has a main face on which an concave and convex portion is formed, a group-III nitride compound semiconductor layer that is formed on the main face of the substrate, and a clearance that is formed between the substrate and the group-III nitride compound semiconductor layer at a first region of the semiconductor light emitting element. In the first region, a portion of the group-III nitride compound semiconductor layer and a portion of the clearance are disposed in a concave of the concave and convex portion on a section through two adjacent top portions of the concave and convex portion and a bottom portion located between the adjacent top portions.