Patterned Substrate Holes for Light Extraction in LED Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor light-emitting devices face inefficiencies in light extraction due to waveguide formation between the substrate and semiconductor material, leading to trapped light, which can be addressed by modifying the substrate surface with features and coatings to enhance light transmission and direction control.
Innovation Solution
The substrate features, such as holes with specific orientations and coatings like SiN, form a gradient index optical interface between the semiconductor and substrate, allowing for improved light extraction by scattering and directing emitted light, while minimizing impact on crystal growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a smooth substrate surface is used, then crystal growth quality is maintained, but light extraction efficiency is poor due to waveguide formation
Solution Approach 1:
The substrate surface is modified with localized features (holes or grooves) at specific positions rather than being uniformly smooth. These localized modifications create gradient index optical interfaces that scatter light and improve extraction efficiency only in specific regions, while the overall crystal growth quality on the majority of the substrate surface is preserved.
Solution Approach 2:
A gradient index optical interface is introduced as an intermediary between the high refractive index semiconductor material and the substrate. This gradient index layer (with refractive index transitioning from higher near the semiconductor to lower near the substrate) acts as a mediator that reduces total internal reflection and improves light extraction without requiring a completely rough substrate surface that would harm crystal growth.
2Loss of energy
If substrate surface features are added to improve light extraction, then light scattering increases, but device complexity increases
Solution Approach 1:
The substrate surface is segmented into multiple discrete features (holes or grooves) arranged in a pattern rather than being a single continuous structure. This segmentation allows for controlled light scattering while maintaining manufacturing feasibility through standard photolithography and etching processes, balancing performance improvement with device complexity management.
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 approach increases light extraction efficiency by scattering trapped light and controlling its direction, reducing energy loss and enhancing the far-field emission of semiconductor light-emitting devices.
Implementation Method 1
This approach increases light extraction efficiency by scattering trapped light and controlling its direction
Implementation Method 2
The non-III-nitride material is a stack of layers that forms a gradient index optical interface between the semiconductor and the substrate. The gradient index optical material interface smoothly transitions from a high refractive index to a low refractive index.
Data Source
Figure 1~3
Figure 4~6
AI summary
A lighting device according to embodiments of the invention includes a substrate with a plurality of holes that extend from a surface of the substrate. A non-III- nitride material is disposed within the plurality of holes. The surface of the substrate is free of the non-III-nitride material. A semiconductor structure is grown on the surface of the substrate. The semiconductor structure includes a light emitting layer disposed between an n- type region and a p-type region.