Nitride LED with Patterned Substrate and Low-Index Blocking Layer
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Solution Overview
Problem
Current nitride LEDs face challenges in achieving high light extraction efficiency and internal quantum efficiency, limiting their light output power.
Innovation Solution
A nitride LED structure is developed with a substrate featuring sub-micro patterns and a growth blocking layer of lower refractive index than the light-emitting epitaxial layer, forming an undulating morphology that increases the light extraction interface and refractive index difference, enhancing light extraction efficiency through lateral epitaxy and compound reflective substrate design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional planar substrate and epitaxial structure are used, then the device structure is simple and easy to manufacture, but the light extraction efficiency and internal quantum efficiency are low
Solution Approach 1:
The substrate surface is designed with sub-micro patterns (convex and concave structures) instead of a planar surface. These curved/undulating surfaces increase light scattering and extraction efficiency by creating multiple reflection paths, directly resolving the contradiction between manufacturing simplicity and light extraction performance
Solution Approach 2:
The refractive index of the growth blocking layer is specifically controlled to be lower than that of the light-emitting epitaxial layer. This parameter optimization creates favorable optical conditions for light extraction while maintaining structural simplicity, addressing the efficiency-manufacturability trade-off
2Ease of manufacture
If the growth blocking layer has the same refractive index as the light-emitting epitaxial layer, then the material selection is flexible and manufacturing is easier, but the refractive index difference at the light extraction interface is insufficient
Solution Approach 1:
The refractive index of the growth blocking layer is specifically optimized to be lower than that of the light-emitting epitaxial layer. This parameter change creates a favorable refractive index gradient that enhances light extraction efficiency while maintaining manufacturing feasibility through standard material selection
3Device complexity
If the epitaxial layer is grown only in the growth region, then the growth process is simple and controlled, but the light extraction interface area is limited
Solution Approach 1:
The light-emitting epitaxial layer is designed to extend laterally from the growth region into the non-growth region, covering the growth blocking layer. This dimensional extension increases the light extraction interface area without complicating the growth process, as the lateral extension occurs naturally during controlled epitaxial growth
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
The solution significantly improves light extraction efficiency and internal quantum efficiency, leading to increased light output power and reduced defect density in nitride LEDs.
Implementation Method 1
the refractive index of the growth blocking layer is less than that of the light-emitting epitaxial layer and the growth blocking layer forms undulating morphology along the sub-micro patterns of the substrate, thus increasing light extraction interface of LED, generating refractive index difference between the light-emitting epitaxial layer and the light extraction interface and improving light extraction efficiency
Implementation Method 2
the non-growth region has powerful light reflection effect. And the growth region is also capable of reflection through the sub-micro patterned sapphire substrate, thus constituting a complete and compound reflective substrate
Implementation Method 3
a light-emitting epitaxial layer, comprising an n-type layer, a light-emitting layer and a p-type layer
Data Source
AI summary
A nitride light-emitting diode including: a substrate with sub-micro patterns over the surface, which is divided into a growth region and a non-growth region; a growth blocking layer, formed in the non-growth region of the substrate for blocking epitaxial growth in the non-growth region of the substrate; a light-emitting epitaxial layer, comprising an n-type layer, a light-emitting layer and a p-type layer, formed in the growth region of the substrate, which extends to the non-growth region through lateral epitaxy and covers the growth blocking layer; wherein, the refractive index of the growth blocking layer is less than that of the light-emitting epitaxial layer and the growth blocking layer forms undulating morphology along the sub-micro patterns of the substrate, thus increasing light extraction interface of LED, generating refractive index difference between the light-emitting epitaxial layer and the light extraction interface and improving light extraction efficiency.