Nitride Semiconductor LED Stacked Structures for Dislocation Reduction
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Solution Overview
Problem
Nitride semiconductor-based semiconductor light emitting devices face challenges in achieving high light emission efficiency due to high density threading dislocations caused by lattice mismatch, limiting their optical output power.
Innovation Solution
The semiconductor light emitting device incorporates a specific layered structure comprising n-type and p-type nitride semiconductor layers, a light emitting unit with barrier and well layers, and stacked structures with alternating layers of AlGaInN and GaInN, optimized to reduce strain and improve crystal quality, which are fabricated using metal organic chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitride semiconductor layers are used for light emitting devices, then the device can be manufactured with standard processes, but high density threading dislocations occur due to lattice mismatch with GaN crystal
Solution Approach 1:
The patent segments the crystal structure into alternating layers of GaInN and AlGaInN with different lattice constants. This segmentation creates a superlattice structure where each layer is thinner than the critical thickness, preventing dislocation propagation while maintaining manufacturability through standard semiconductor processes
Solution Approach 2:
The AlGaInN layers act as intermediary layers between GaInN layers, serving as dislocation blocking barriers. These intermediary layers have different lattice constants that prevent the propagation of threading dislocations while allowing the overall structure to be manufactured using conventional nitride semiconductor fabrication processes
2Power
If output power is increased in nitride semiconductor LED devices, then higher optical output is achieved, but light emission efficiency decreases
Solution Approach 1:
The patent extracts and removes threading dislocations from the crystal structure by using alternating layers with different lattice constants. The AlGaInN layers specifically extract and block dislocation propagation paths, enabling high optical output without the efficiency loss that normally accompanies increased power in conventional nitride LEDs
3Reliability
If alternating layers of GaInN and AlGaInN are stacked with each layer thinner than critical thickness, then dislocation propagation is prevented, but device structure becomes more complex
Solution Approach 1:
The patent uses composite material structure with alternating GaInN and AlGaInN layers, where each material contributes specific properties. The GaInN layers provide light emitting functionality while AlGaInN layers provide dislocation blocking, creating a composite structure that achieves low dislocation density without excessive complexity through systematic layering
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 enhances light emission efficiency by reducing dislocation density and improving crystal quality, leading to higher optical output and better controllability of emission wavelength and intensity.
Implementation Method 1
the characteristics of such nitride semiconductor devices are restricted by high density threading dislocations due to lattice mismatch with the GaN crystal
Implementation Method 2
which are fabricated using metal organic chemical vapor deposition
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes a first layer of n-type and a second layer of p-type including a nitride semiconductor, a light emitting unit provided between the first and second layers, a first stacked structure provided between the first layer and the light emitting unit, and a second stacked structure provided between the first layer and the first stacked structure. The light emitting unit includes barrier layers and a well layer provided between the barrier layers. The first stacked structure includes third layers including a nitride semiconductor, and fourth layers stacked with the third layers and including GaInN. The fourth layers have a thinner thickness than the well layer. The second stacked structure includes fifth layers including a nitride semiconductor, and sixth layers stacked with the fifth layers and including GaInN. The sixth layers have a thinner thickness than the well layer.