Nitride Semiconductor LED With Graded Indium Ratios
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nitride semiconductor light emitting diodes face challenges in achieving high luminous efficiency due to self-absorption issues in active layers, particularly in multi-quantum well structures, while single quantum well structures struggle to match the efficiency of multi-quantum well structures.
Innovation Solution
A nitride semiconductor light emitting diode structure is developed with an active layer surrounded by second and third nitride semiconductor layers, each containing an InGaN layer with a lower Indium ratio than the active layer, forming a periodic structure to enhance light extraction efficiency and internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multi-quantum well structure is used in the active layer, then internal quantum efficiency is improved, but light extraction efficiency deteriorates due to self-absorption
Solution Approach 1:
The patent applies local quality by creating distinct regions with different Indium ratios: the active layer maintains high Indium ratio (20-30%) for high internal quantum efficiency, while the cladding layers use lower Indium ratios (5-15%) to reduce self-absorption. This spatial differentiation of material composition allows each region to optimize for its specific function.
Solution Approach 2:
The active layer is segmented into multiple quantum well structures separated by barrier layers, with each well layer contributing to light emission. The cladding layers are further segmented into multiple sub-layers with varying Indium ratios, creating a graded structure that progressively reduces self-absorption while maintaining carrier confinement.
2Loss of energy
If a single quantum well structure is used in the active layer, then self-absorption is reduced, but internal quantum efficiency deteriorates
Solution Approach 1:
The single quantum well is replaced with multiple quantum well segments (at least 2 wells), where each well layer is separated by barrier layers. This segmentation allows the structure to maintain reduced self-absorption characteristics while increasing the total active volume for carrier recombination and light emission, thereby improving internal quantum efficiency.
Solution Approach 2:
The patent extends the structure into the vertical dimension by stacking multiple quantum well layers at different heights, rather than relying on a single planar well. This dimensional expansion increases the effective emission volume while maintaining the low self-absorption benefits of the single-well approach.
3Use of energy by moving object
If the Indium ratio in cladding layers is increased to match the active layer, then internal quantum efficiency is improved, but light extraction efficiency deteriorates
Solution Approach 1:
The cladding layers are assigned a different local quality (lower Indium ratio of 5-15%) compared to the active layer (higher Indium ratio of 20-30%). This quality differentiation ensures that the cladding regions do not exhibit strong absorption at the emission wavelength, allowing light generated in the active layer to extract efficiently through the cladding layers.
Solution Approach 2:
The Indium ratio parameter is changed between different layers: high Indium content in the active layer optimizes for carrier confinement and radiative recombination, while low Indium content in the cladding layers optimizes for light transmission. This parameter optimization in each region resolves the contradiction between internal quantum efficiency and light extraction efficiency.
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 luminous efficiency by reducing self-absorption and achieving higher light extraction efficiency compared to both multi-quantum well and single quantum well structures, with the InGaN layers in the second and third nitride semiconductor layers having In ratios between 5% to 15% for optimal performance.
Implementation Method 1
One of the factors of deterioration in luminous efficiency of a light emitting diode is deterioration in light extraction efficiency due to self absorption of an active layer
Implementation Method 2
nitride semiconductor light emitting diode including at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer
Data Source
AI summary
A nitride semiconductor light emitting diode includes at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer. The active layer is formed of one first nitride semiconductor layer having a highest In ratio in the light emitting diode. The light emitting diode further includes at least one of a second nitride semiconductor layer located between the active layer and the n-type nitride semiconductor layer and including an InGaN layer, and a third nitride semiconductor layer located between the active layer and the p-type nitride semiconductor layer and including an InGaN layer. Respective In (Indium) ratios of the InGaN layers included in the second nitride semiconductor layer and the InGaN layers included in the third nitride semiconductor layer are lower than the In ratio of the first nitride semiconductor layer forming the active layer. The LED with high luminous efficiency can thus be provided.