Red LED Superlattice P-Cladding for Mg Diffusion Control
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Solution Overview
Problem
Red light emitting diodes (LEDs) face challenges in achieving high optical power and reliability, particularly due to magnesium diffusion phenomena and luminous intensity drops with temperature increases, which affect their performance in applications such as high color rendering index lighting and vehicle lighting.
Innovation Solution
The implementation of a red light emitting device with a superlattice structure in the p-type GaP layer, including a GaP layer doped with a higher concentration of Mg and an InxGa1-xP layer with a lower dopant concentration, along with a superlattice structure in the AlInP series layer to enhance electron cooling and radiation recombination, and the use of intermediate semiconductor layers to reduce strain and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional red LED structure is used, then the device is simple to manufacture, but the optical power and reliability are insufficient
Solution Approach 1:
The p-type cladding layer is segmented into multiple sub-layers with different compositions and doping concentrations. Specifically, it includes a first p-type cladding layer (AlGaInP), a second p-type cladding layer (GaInP), and a third p-type cladding layer (GaP), each with progressively lower Al content and optimized Mg doping. This segmentation allows independent optimization of each layer's properties to suppress magnesium diffusion while maintaining structural integrity and manufacturability.
Solution Approach 2:
Different regions of the p-type cladding layer are assigned different local qualities through varying composition and doping. The first p-type cladding layer has higher Al content and Mg doping to provide initial confinement, the second layer has intermediate properties for transition, and the third layer has lowest Al content with optimized doping to suppress Mg diffusion at the interface. This local quality variation enables targeted suppression of magnesium diffusion without requiring complete structural redesign.
2Reliability
If the Mg doping concentration in the p-type GaP layer is increased to suppress diffusion, then reliability improves, but luminous intensity drops due to temperature increases
Solution Approach 1:
The invention optimizes the Mg doping concentration parameter in the p-type GaP layer (third p-type cladding layer) to a specific range that balances diffusion suppression and luminous intensity maintenance. Additionally, the Al composition ratio is progressively reduced from the first to third p-type cladding layer, creating a gradient structure that manages strain and thermal effects. These parameter optimizations ensure sufficient Mg diffusion suppression while minimizing temperature-induced luminous intensity drops.
Solution Approach 2:
The p-type cladding structure uses a composite of three different semiconductor materials (AlGaInP, GaInP, and GaP) with progressively changing compositions. This composite structure combines the advantages of each material: AlGaInP provides initial confinement, GaInP provides transition with strain management, and GaP provides effective Mg diffusion suppression. The composite approach achieves both high reliability and maintained luminous intensity under temperature variation.
3Reliability
If a superlattice structure is implemented in the p-type GaP layer, then magnesium diffusion is minimized, but the manufacturing process becomes more complex
Solution Approach 1:
Rather than implementing a complex superlattice structure, the invention segments the p-type cladding into three distinct layers with progressively optimized properties. This segmentation achieves the diffusion suppression function of a superlattice through a simpler, more manufacturable approach using conventional layer-by-layer growth techniques with controlled composition and doping gradients.
Solution Approach 2:
The invention uses parameter changes (composition ratio and doping concentration gradients across the three p-type cladding layers) to achieve diffusion suppression without requiring the complex periodic superlattice structure. This parameter optimization approach maintains compatibility with standard manufacturing processes while achieving the desired reliability improvement.
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 increases luminous intensity by 1.5% or more and enhances reliability by minimizing the magnesium diffusion effect and temperature-induced luminous intensity drops, thereby improving the overall performance of the red light emitting device.
Implementation Method 1
a second conductive type fifth semiconductor layer (125) on the second conductive type fourth semiconductor layer (124). The second conductive type fifth semiconductor layer (125) may include a superlattice structure of a GaP layer (125a)/InxGa1-xP layer (0≤x≤1) (125b)
Implementation Method 2
a superlattice structure in the AlInP series layer to enhance electron cooling and radiation recombination
Implementation Method 3
A light emitting diode (LED) is a p-n junction diode having a characteristic in which electric energy is converted into light energy
Data Source
AI summary
A red light emitting device, a fabricating method of the light emitting device, a light emitting device package and a lighting system are provided. The red light emitting device according to an embodiment may include a first conductive type first semiconductor layer 112; an active layer 114 on the first conductive type first semiconductor layer 112; a second conductive type third semiconductor layer 116 on the active layer 114; a second conductive type fourth semiconductor layer 124 on the second conductive type third semiconductor layer 116; and a second conductive type fifth semiconductor layer 125 on the second conductive type fourth semiconductor layer 124. The second conductive type fifth semiconductor layer 125 may include a superlattice structure of a GaP layer 125a/InxGa1-xP layer (0≤x≤1) 125b.