GaN LED Dome Cap for Light Extraction
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Solution Overview
Problem
Gallium Nitride LEDs face challenges in extracting light due to the difficulty in growing thick and conductive p-type AlInGaN layers, resulting in a limited light-emitting area and inefficient light extraction, with prior art devices having practical limitations in mesa height and fill-factor for active regions.
Innovation Solution
The implementation of a light emitting structure with an integrated transparent electrically conductive dome-shaped cap layer that enhances light extraction by reducing Fresnel reflections and shaping the current distribution, combined with textured surfaces and reflective layers to guide light angles below the critical angle, thereby increasing the amount of extracted radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat truncated top structure is used in GaN LEDs, then the manufacturing is simpler, but the usable active area for light extraction becomes small and the fill-factor becomes negligible
Solution Approach 1:
The patent applies a curved, dome-shaped transparent cap structure on top of the LED instead of a flat truncated top. This curvature increases the usable active area for light extraction while maintaining manufacturing feasibility through epitaxial growth processes. The dome shape provides a larger surface area for light emission compared to a flat surface of the same footprint.
2Ease of manufacture
If the quantum well is placed close to the top surface (within 500 nm), then the light emitting area can be formed, but the light extraction efficiency is reduced due to the small escape cone angle
Solution Approach 1:
The dome-shaped transparent cap structure modifies the light extraction geometry by providing a curved interface between the semiconductor and external environment. This curvature changes the angle of incidence for light rays, effectively increasing the escape cone angle and reducing total internal reflection losses at the surface.
Solution Approach 2:
The patent changes the geometric parameters of the light extraction interface by introducing a curved surface with specific radius of curvature. This parameter change optimizes the balance between maintaining the quantum well close to the surface (for manufacturing ease) and improving light extraction efficiency (by modifying the escape cone geometry).
3Reliability
If thick p-type AlInGaN layers are grown to improve conductivity, then the electrical performance improves, but the growth difficulty increases significantly compared to n-type layers
Solution Approach 1:
Instead of attempting to grow very thick p-type layers (which would improve conductivity but are extremely difficult), the patent uses a moderate thickness p-type layer combined with the dome-shaped structure to achieve the desired electrical performance. The curved geometry compensates for the limited thickness by optimizing the extraction path for the available charge carriers.
4Productivity
If the light emitting volume is made very small to increase the fill-factor, then the active region efficiency improves, but the overall light output is reduced
Solution Approach 1:
The patent transitions from a two-dimensional planar light extraction geometry to a three-dimensional dome-shaped structure. This dimensional change allows the light emitting volume to be small (maintaining high fill-factor) while the curved surface provides a larger effective emission area, thereby increasing overall light output through optimized spatial distribution.
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 significantly improves light extraction efficiency by reducing surface recombination and absorption, allowing for a larger active light-emitting area and increased light output, overcoming the limitations of traditional LED structures.
Implementation Method 1
the integrated transparent electrically conductive layer improves the amount of light capable of being extracted from the light emitting structure
Implementation Method 2
a light emitter capable of emitting electromagnetic radiation; a light generating quantum well region
Implementation Method 3
guide light angles below the critical angle, thereby increasing the amount of extracted radiation; For a GaN-air interface the critical angle is only 21°, 24° and 25° at the wavelengths of 365, 450 and 520 nm, respectively
Data Source
AI summary
There is herein described light generating electronic components with improved light extraction and a method of manufacturing said electronic components. More particularly, there is described LEDs having improved light extraction and a method of manufacturing said LEDs.