Nitride Semiconductor Light-Emitting Element With Graded Electron Blocking Layers
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Solution Overview
Problem
Nitride semiconductor light-emitting elements face challenges in extending emission life while improving luminous efficiency due to lattice mismatch and quality deterioration caused by high Al composition ratios in electron blocking layers.
Innovation Solution
A nitride semiconductor light-emitting element with a p-type AlGaN-based electron blocking stack body comprising a first electron blocking layer, a second electron blocking layer with a lower Al composition ratio, and a third electron blocking layer with a decreasing Al composition ratio from the second electron blocking layer toward the p-type contact layer, reducing lattice mismatch and enhancing hole injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electron blocking layer is formed with a high Al composition ratio to increase electron injection efficiency, then luminous efficiency is improved, but lattice mismatch increases causing quality deterioration and reduced emission lifetime
Solution Approach 1:
The electron blocking layer is divided into three distinct layers (first, second, and third electron blocking layers) with different Al composition ratios. The first layer has high Al composition for strong electron blocking and high luminous efficiency, while the second and third layers have progressively lower Al composition to reduce lattice mismatch with the p-type contact layer, thereby extending emission lifetime.
Solution Approach 2:
Different regions of the electron blocking layer are assigned different Al composition ratios tailored to their specific functions. The first electron blocking layer (adjacent to the light-emitting layer) uses high Al composition for optimal electron blocking performance, while the third electron blocking layer (adjacent to the p-type contact layer) uses lower Al composition to minimize lattice mismatch and improve interface quality.
2Power
If the Al composition ratio difference between the electron blocking layer and p-type contact layer is large to improve electron injection, then luminous efficiency increases, but crystal defects increase reducing emission lifetime
Solution Approach 1:
The Al composition ratio is progressively changed across the three electron blocking layers, transitioning from high Al composition in the first layer to lower Al composition in the second and third layers. This gradual parameter change reduces the abruptness of composition transitions at interfaces, minimizing crystal defects and improving overall crystal quality while maintaining effective electron blocking.
Data Source
AI summary
A nitride semiconductor light-emitting element includes an active layer that emits ultraviolet light, a p-type AlGaN-based electron blocking stack body that is located on the active layer and has a structure formed by sequentially stacking a first electron blocking layer, a second electron blocking layer and a third electron blocking layer from the active layer side, and a p-type contact layer located on the electron blocking stack body. An Al composition ratio in the second electron blocking layer is lower than an Al composition ratio in the first electron blocking layer, and an Al composition ratio in the third electron blocking layer decreases from the second electron blocking layer side toward the p-type contact layer side.