UV LED Chip Microstructure for Higher Light Extraction
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Solution Overview
Problem
Current surface roughening techniques for LED chips are insufficient in enhancing light extraction efficiency, and conventional LED electrodes and substrate or metal layers can block or absorb light, further reducing efficiency.
Innovation Solution
The LED chip features a substrate with an epitaxial structure that includes a microstructure on the light-emitting surface, comprising first and second protrusions that scatter light and reduce internal reflection, thereby enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If surface roughening is performed by forming microstructures on the light-exiting surface, then light extraction efficiency is improved, but the light extraction efficiency is still insufficient to achieve optimal performance
Solution Approach 1:
The light-exiting surface is segmented into multiple hierarchical microstructure layers: a first microstructure layer with first protrusions and recesses, and a second microstructure layer with second protrusions and recesses. This segmentation creates multiple interfaces for light scattering, significantly improving light extraction efficiency beyond conventional single-layer roughening techniques.
Solution Approach 2:
The patent introduces a vertical dimension to light scattering by creating hierarchical microstructures at different depths and scales. The first and second microstructure layers are disposed at different positions along the vertical axis, adding a depth dimension to the traditional surface-level roughening approach, thereby creating more scattering opportunities for light paths.
2Ease of operation
If LED electrodes and substrate or metal layers are present on or near the light-exiting surface, then electrical functionality is provided, but light is blocked or absorbed, reducing light emitting efficiency
Solution Approach 1:
The microstructures are designed with varying local properties: the first protrusions have different dimensions than the second protrusions, and they are distributed at different densities in different regions. This local variation optimizes light scattering in different zones while accommodating electrode placements, reducing light blocking while maintaining electrical functionality.
Solution Approach 2:
The microstructure layers act as intermediary elements between the light-generating active layer and the external environment. They provide a transition zone that scatters light effectively while allowing electrode integration, mediating between the conflicting requirements of light extraction and electrical connectivity.
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 microstructured light-emitting surface effectively increases light extraction efficiency by scattering light and reducing internal reflection, while minimizing light blocking or absorption by electrodes and substrate layers.
Implementation Method 1
The microstructures allow incident light at an angle greater than critical angle to be scattered to exit the LED
Implementation Method 2
The microstructures allow incident light at an angle greater than critical angle to be scattered to exit the LED
Data Source
AI summary
A light-emitting diode (LED) chip includes a substrate and an epitaxial structure. The epitaxial structure includes a first semiconductor layer, an active layer and a second semiconductor layer that are sequentially disposed on the substrate in such order. The second semiconductor layer has a light-emitting surface that is opposite to the active layer and that is formed with a microstructure. The microstructure includes a plurality of first protrusions that are separately disposed on the light-emitting surface, and a plurality of second protrusions that are disposed on the first protrusions and on the light-emitting surface between any two adjacent ones of the first protrusions.