GaN Light-Emitting Layer Structure for Lower Threading Dislocations
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Solution Overview
Problem
Light emitting devices using gallium nitride (GaN) based materials face challenges in achieving high light emission efficiency, particularly in the green band and at high temperatures, due to issues with lattice mismatch and crystal defects.
Innovation Solution
A light emitting device structure is developed with a three-layer configuration, where the first layer has a larger lattice constant than GaN, the second layer is lattice relaxed with respect to the first layer, and the third layer, which includes an active layer, has an even larger lattice constant, optimizing the lattice constants to reduce crystal defects and enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light emitting layer with a lattice constant larger than the substrate is used, then light emission in green band can be achieved, but threading dislocations increase and light emission efficiency decreases
Solution Approach 1:
The patent divides the light emitting layer into multiple segments with different In compositions (first light emitting layer with 20-30% In, second light emitting layer with 30-40% In). This segmentation allows each layer to accommodate different lattice constants, reducing overall threading dislocation density while maintaining green band light emission capability.
Solution Approach 2:
The patent applies local quality by creating regions with different In compositions within the light emitting layer. The first light emitting layer has lower In content (20-30%) closer to the GaN substrate, while the second light emitting layer has higher In content (30-40%) further from the substrate. This local variation in composition optimizes lattice matching at different depths, reducing threading dislocations while enabling efficient green light emission.
2Illumination intensity
If GaInN based material is used for green band emission, then green light can be emitted, but light emission efficiency is low at high temperature
Solution Approach 1:
The patent changes the compositional parameters of the light emitting layers by using a gradient In composition (20-30% in first layer, 30-40% in second layer) rather than a uniform composition. This parameter variation optimizes the material properties for high temperature operation while maintaining green band light emission, as the lower In content regions provide thermal stability while higher In content regions enhance light emission efficiency.
3Illumination intensity
If In composition is increased to achieve green band emission, then wavelength is shifted to green, but light emission efficiency decreases due to increased non-radiative recombination
Solution Approach 1:
The patent segments the light emitting layer into two distinct regions with different In compositions. The first light emitting layer (20-30% In) has lower non-radiative recombination loss, while the second light emitting layer (30-40% In) provides the necessary green band wavelength. This segmentation allows the structure to achieve green emission while minimizing overall energy loss through non-radiative recombination.
Solution Approach 2:
The patent creates a composite light emitting structure combining GaInN layers with different In compositions. This composite approach allows the structure to leverage the advantages of both lower In content (reduced non-radiative recombination) and higher In content (green band emission), achieving a balance between wavelength control and emission efficiency.
Data Source
AI summary
A light emitting device according to an embodiment of the present disclosure includes: a first layer including Alx2Inx1Ga(1-x1-x2) N (0<x1<1, 0≤x2<1); a second layer that is provided on the first layer and includes Aly2Iny1Ga(1-y1-y2) N (0<y1<1, 0≤y2<1) that is lattice relaxed with respect to the first layer; and a third layer that is provided on the second layer, includes Alz2Inz1Ga(1-z1-z2) N (0<z1<1, 0≤z2<1) that is lattice relaxed with respect to the second layer, and includes an active layer. A lattice constant aGAN of GaN in an in-plane direction, a lattice constant al of the first layer in an in-plane direction, a lattice constant a2 of the second layer in an in-plane direction, and a lattice constant a3 of the third layer in an in-plane direction have a relationship of aGAN<a2<a1, a3.