Segmented Current Spreading Layers for LED Light Extraction
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Solution Overview
Problem
Current solid-state lighting devices, such as LEDs, face limitations in light emission efficiency due to internal reflection and current spreading issues, particularly for larger area LEDs, which hinder the extraction of light and efficient current distribution.
Innovation Solution
The implementation of current spreading layer structures in LED chips, featuring openings in dielectric reflector layers that allow metal reflector layers and reflective interconnects to form interfaces with active LED structures, enhancing current injection and light extraction by creating discontinuous regions and varying reflective layer interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a continuous current spreading layer is used to improve current distribution, then current spreading efficiency is improved, but light extraction is reduced due to blocking of light paths
Solution Approach 1:
The current spreading layer is segmented into multiple discrete regions rather than being continuous. These segmented regions allow light to pass through to the dielectric reflector layer while still providing sufficient current spreading across the LED chip surface, thereby resolving the contradiction between current distribution and light extraction efficiency
2Illumination intensity
If the LED active region area is increased to improve light output, then illumination capacity is improved, but current spreading becomes insufficient leading to reduced efficiency
Solution Approach 1:
The current spreading layer is strategically positioned in specific regions where current distribution is most needed, rather than uniformly covering the entire large area. This localized approach maintains high current spreading efficiency while accommodating larger LED active regions for increased light output
3Loss of energy
If reflective layers are added to improve light extraction, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The segmented current spreading layer regions serve dual functions: they allow light extraction paths to reach the dielectric reflector layer, and simultaneously provide current spreading functionality. This multi-functionality reduces the need for separate reflective structures, thereby improving light extraction while minimizing additional device complexity
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 improves light extraction and current spreading efficiency, allowing for more effective directional light emission and increased illumination characteristics, overcoming the limitations of conventional LEDs.
Implementation Method 1
Reflective surfaces may also be provided to reflect generated light so that such light may contribute to useful emission from an LED chip. LEDs have been developed with internal reflective surfaces or layers to reflect generated light.
Implementation Method 2
To increase current spreading for LEDs, and in particular for larger area LEDs, it has been found useful to add layers of high electrical conductivity over one or more epitaxial layers of an LED.
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and more particularly current spreading layer structures for LED chips are disclosed. LED chips include active LED structures with current spreading layer arrangements relative to reflective structures that provide efficient current injection into the active LED structures while also providing improved light extraction. Current spreading layers include openings that allow portions of dielectric reflector layers to form interfaces with active LED structures adjacent the current spreading layers. Metal reflector layers are provided on the dielectric reflector layers, and reflective layer interconnects are formed through the dielectric reflector layers to contact portions of the current spreading layer.