Porous LED Structure With Quantum Dot Conversion for Red Color Purity
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in achieving high optical efficiency and color purity, particularly when emitting red light, due to lattice mismatch defects and blue shift phenomena, which reduce external quantum efficiency and lead to defects and agglomeration issues with high indium content in active layers.
Innovation Solution
A light emitting device is designed with a porous first type semiconductor layer, an active layer, and a second type semiconductor layer, incorporating a wavelength conversion cluster of quantum dots embedded in the porous layer to convert ultraviolet to blue light into green or red light, along with a wavelength selective transmission layer and reflective layers to enhance light emission and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high indium content is used in the active layer to achieve red light emission, then the emission wavelength is extended to red region, but lattice mismatch defects and blue shift phenomena increase, reducing external quantum efficiency
Solution Approach 1:
The patent employs a porous GaN layer as the first cladding layer with controlled porosity (10-50%). This porous structure reduces the indium content requirement in the active layer while maintaining red light emission capability. The porous structure modifies the optical and electrical properties, allowing efficient red light emission without the severe lattice mismatch defects that occur in conventional high-indium active layers.
Solution Approach 2:
The patent changes the physical and chemical parameters of the cladding layers, specifically introducing porosity in the first cladding layer and controlling the thickness and composition of both cladding layers. These parameter changes enable the active layer to emit red light with high external quantum efficiency by optimizing the strain distribution and optical confinement, avoiding the blue shift phenomenon associated with high indium content.
2Ease of manufacture
If conventional LED structures are used for red light emission, then manufacturing is simpler, but color purity is reduced due to defects and blue shift
Solution Approach 1:
The porous first cladding layer provides a straightforward manufacturing approach using standard semiconductor fabrication techniques. The porosity is introduced through controlled etching processes that are compatible with existing LED manufacturing lines. This structure achieves high color purity red light emission without requiring complex multi-quantum well structures or specialized growth conditions.
Solution Approach 2:
The patent uses a composite structure with two different cladding layers: a porous GaN first cladding layer and a non-porous GaN or AlGaN second cladding layer. This composite approach combines the advantages of both porous (strain relief, optical confinement) and conventional (structural stability, ease of fabrication) structures, achieving high color purity while maintaining manufacturing simplicity.
3Reliability
If porous structure is introduced to improve color purity and reduce defects, then optical efficiency increases, but device complexity increases
Solution Approach 1:
The porous structure is introduced only in the first cladding layer, not throughout the entire device. This localized porosity approach improves optical efficiency and reduces defects in the critical region near the active layer, while keeping the rest of the device structure conventional and simple. The porosity gradient and controlled distribution minimize the impact on device fabrication complexity.
Solution Approach 2:
The patent applies different properties to different regions: the first cladding layer has porous structure for strain relief and optical confinement, while the second cladding layer maintains conventional dense structure for structural stability. This local differentiation optimizes performance in each region without requiring the entire device to be complex, balancing optical efficiency with manufacturing feasibility.
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 solution effectively increases color purity and reduces defects by converting light within the LED, improving optical efficiency and reducing blue shift effects, while maintaining low indium content in the active layer to minimize lattice mismatch issues.
Implementation Method 1
a wavelength conversion cluster embedded in the porous first type semiconductor layer, the wavelength conversion cluster being configured to convert a first light generated in the active layer into a second light having a different wavelength. The wavelength conversion cluster may include quantum dots converting the first light into the second light
Implementation Method 2
The wavelength selective transmission layer may include a distributed Bragg reflector
Implementation Method 3
The wavelength selective transmission layer may include a distributed Bragg reflector
Data Source
AI summary
A light emitting device includes a light emitting rod in which a porous first type semiconductor layer, an active layer, and a second type semiconductor layer are sequentially arranged, and a wavelength conversion cluster is embedded in the porous first type semiconductor layer and configured to convert a first light generated in the active layer into a second light having a different wavelength.