Laser Light-Emitting Structure With Buffer Layer for Crystal Quality
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Solution Overview
Problem
Existing light emitting devices face challenges in maintaining high reliability due to deteriorated crystallizability and increased light absorption in contact layers with high carrier concentrations, which affect laser oscillation characteristics and manufacturing yield.
Innovation Solution
Incorporating a buffer layer with a different carrier concentration, material composition, or composition ratio between the first contact layer and the semiconductor stacked body to alleviate crystallizability deterioration and maintain crystal quality, while reducing light absorption and increasing design freedom in film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the carrier concentration of the first contact layer is increased to improve electrical conductivity, then the electrical conductivity is improved, but the crystal quality of the semiconductor stacked body deteriorates and light absorption increases
Solution Approach 1:
The contact layer structure is segmented into multiple layers with different carrier concentrations. The first contact layer has high carrier concentration for good electrical conductivity, while the second contact layer has lower carrier concentration to prevent crystal quality deterioration and reduce light absorption. This segmentation allows each layer to optimize its function independently.
Solution Approach 2:
Different regions of the contact layer structure are assigned different carrier concentrations based on their specific functional requirements. The first contact layer region requires high carrier concentration for conductivity, while the second contact layer region requires lower carrier concentration for crystal quality. This local quality differentiation resolves the contradiction between conductivity and crystal quality.
2Reliability
If the carrier concentration of the first contact layer is increased to improve electrical conductivity, then the electrical conductivity is improved, but light absorption increases
Solution Approach 1:
The contact layer is segmented into two layers with different carrier concentrations. The first contact layer maintains high carrier concentration for electrical conductivity, while the second contact layer uses lower carrier concentration to minimize light absorption. This segmentation separates the conductivity function from the light transmission function.
Solution Approach 2:
The second contact layer is designed with locally different properties (lower carrier concentration) specifically to reduce light absorption in regions where light passes through, while the first contact layer maintains high carrier concentration for conductivity where needed.
3Reliability
If the film thickness of the first contact layer is increased to improve electrical conductivity, then the electrical conductivity is improved, but the design freedom is reduced
Solution Approach 1:
The contact layer structure is segmented into multiple layers, each with independent thickness and carrier concentration parameters. This segmentation provides multiple design degrees of freedom, allowing optimization of electrical conductivity through one layer while controlling light absorption and crystal quality through other layers.
Solution Approach 2:
By introducing multiple contact layers with different carrier concentrations, the design space is expanded. Each layer's thickness and carrier concentration can be independently adjusted, providing greater design freedom to simultaneously satisfy multiple requirements (conductivity, light absorption, crystal quality) that would be conflicting in a single-layer structure.
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A light emitting device according to an embodiment of the present disclosure includes: a substrate; a first contact layer; a buffer layer in which at least any of a carrier concentration, a material composition, and a composition ratio is different from that of the first contact layer; and a semiconductor stacked body. The substrate has a first surface and a second surface that are opposed to each other. The first contact layer is stacked on the first surface of the substrate. The buffer layer is stacked on the first contact layer. The semiconductor stacked body is stacked above the first surface of the substrate with the first contact layer and the buffer layer interposed in between. The semiconductor stacked body has a light emitting region configured to emit laser light.