Nitride Semiconductor LED Intermediate Layer Dislocation Control
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Solution Overview
Problem
Nitride semiconductor light emitting diodes (LEDs) fabricated on sapphire substrates suffer from high dislocation densities due to lattice constant mismatch, leading to decreased lifetime and efficiency, while using nitride semiconductor substrates like GaN improves light extraction efficiency but often results in increased forward voltage and decreased internal quantum efficiency.
Innovation Solution
Incorporating an intermediate layer with a dislocation generating capability between the substrate and the active layer in nitride semiconductor LEDs, where dislocations from this layer are distributed in the active light emitting region to control dislocation density and improve crystallinity, thereby reducing forward voltage and maintaining high internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a nitride semiconductor layer is grown on a sapphire substrate, then the manufacturing process is simplified, but high dislocation density is generated due to lattice constant mismatch
Solution Approach 1:
An intermediate layer is introduced between the sapphire substrate and the nitride semiconductor layer. This intermediate layer serves as a mediator that reduces lattice mismatch and dislocation generation, enabling the use of sapphire substrates while improving semiconductor layer quality.
2Use of energy by moving object
If a nitride semiconductor substrate is used, then light extraction efficiency is improved, but forward voltage increases and internal quantum efficiency decreases
Solution Approach 1:
The composition ratio of aluminum and indium in the intermediate layer is optimized to balance light extraction efficiency and electrical performance. By controlling the AlxIn1-xN composition, the patent achieves improved light extraction while maintaining acceptable forward voltage and internal quantum efficiency.
3Reliability
If dislocation density in the active layer is reduced, then element lifetime is improved, but light extraction efficiency may be compromised
Solution Approach 1:
The intermediate layer is designed with specific local properties (composition gradient, thickness control) that allow it to reduce dislocations propagating to the active layer while maintaining optical properties for efficient light extraction. The AlxIn1-xN composition is tailored to achieve both mechanical and optical functions.
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 approach enhances light extraction efficiency while preventing increases in forward voltage and decreases in internal quantum efficiency, resulting in LEDs with improved electro-optical characteristics.
Implementation Method 1
Incorporating an intermediate layer with a dislocation generating capability between the substrate and the active layer in nitride semiconductor LEDs, where dislocations from this layer are distributed in the active light emitting region to control dislocation density and improve crystallinity
Implementation Method 2
nitride semiconductor light emitting diode extracting light emitted from the under surface side of the substrate or the upper surface side of the second conductive-type nitride semiconductor layer
Data Source
AI summary
In a nitride semiconductor light emitting diode including a substrate made of a nitride semiconductor, a first conductive-type nitride semiconductor layer formed on the substrate, an active layer made of a nitride semiconductor, and a second conductive-type nitride semiconductor layer, characterized in that light emitted is extracted from the under surface side of the substrate or the upper surface side of the second conductive-type nitride semiconductor layer, an intermediate layer is formed between the substrate and the active layer, and dislocations is allowed to generates from the dislocation generating layer as the origin and to distribute in a light emitting region of the active layer.