Light Extraction Pattern on LED Substrate Sides
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light-emitting devices, particularly lateral LEDs using nitride semiconductors, suffer from low light extraction efficiency due to total reflection at the interface between the patterned sapphire substrate and air, resulting in most light being emitted from the bottom at a predetermined angle and not being utilized effectively.
Innovation Solution
Incorporating a light extraction pattern on the sides of the substrate made of a different material with a higher refractive index than the substrate, such as silicone, to prevent total reflection and enhance light emission from both the top and sides, thereby improving light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a patterned sapphire substrate is used in a lateral LED, then the device structure is simplified and manufacturing is easier, but total reflection at the substrate-air interface causes most light to be trapped and emitted only at predetermined angles, reducing light extraction efficiency
Solution Approach 1:
The patent introduces an extraction structure (such as a microlens array, diffraction grating, or patterned layer) as an intermediary element at the substrate-air interface. This intermediary modifies the optical interaction by refracting, diffracting, or focusing the trapped light waves, enabling them to escape at multiple angles rather than being confined to predetermined directions, thereby improving light extraction efficiency without changing the fundamental patterned sapphire substrate structure
Solution Approach 2:
The patent modifies optical parameters at the substrate interface by introducing structures with different refractive indices, surface geometries, or periodic patterns. These parameter changes alter the critical angle for total internal reflection and create additional light extraction pathways, allowing more light to escape from the substrate while maintaining the ease of manufacturing associated with patterned sapphire substrates
2Illumination intensity
If light is emitted primarily from the bottom of the patterned sapphire substrate at predetermined angles, then the device structure remains simple, but the luminosity and optical output are significantly reduced due to trapped light
Solution Approach 1:
The patent segments the light extraction function by introducing discrete extraction structures (such as individual microlenses, grating elements, or patterned regions) distributed across the substrate surface. Each segment independently modifies local light propagation, collectively enabling omnidirectional light emission and enhanced luminosity while adding minimal overall complexity to the device structure
Solution Approach 2:
The patent addresses the angular confinement of light by introducing extraction structures that operate in additional spatial dimensions. These structures create light extraction pathways in multiple directions and planes, transforming the predominantly vertical, angle-limited emission into omnidirectional emission, thereby significantly improving luminosity without requiring substantial structural 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
The proposed solution increases light extraction efficiency by approximately 16%, allowing for a considerable amount of light to be emitted from the sides of the substrate, leading to enhanced luminosity and improved optical output.
Implementation Method 1
due to the total reflection caused by the difference between the refractive index of the patterned sapphire substrate and the refractive index of the air, most of the light beyond a predetermined critical angle cannot be emitted
Implementation Method 2
the light extraction pattern includes a different material from the substrate
Data Source
AI summary
A light-emitting device, a method of fabricating the light-emitting device, a light-emitting device package and a lighting system are provided. The light-emitting device may include a substrate 105; a first conductivity type semiconductor layer 12 disposed on the substrate 105; an active layer 114 disposed on the first conductivity type semiconductor layer 12; a second conductivity type semiconductor layer 16 disposed on the active layer 114; a first electrode 131 disposed on the first conductivity type semiconductor layer 112; a second electrode 132 disposed on the second conductivity type semiconductor layer 116; a first light extraction pattern P provided on a top surface of the substrate 105; and a second light extraction pattern 150 provided on sides of the substrate 105.