Micro LED Refractive-Index Gradient Layer for Light Extraction
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Solution Overview
Problem
Current GaN-based micro light-emitting diode displays face challenges in achieving optimal light extraction efficiency due to the refractive index mismatch between the n-type III-nitride layers and the cathode transparent electrode, leading to significant light reflection and reduced performance.
Innovation Solution
The micro light-emitting diode device incorporates a second n-type III-nitride layer with a refractive index that monotonically increases from the top to the bottom surface, containing aluminum, which reduces the refractive index difference with the first n-type III-nitride layer and the cathode transparent electrode, enhancing light extraction efficiency by minimizing reflection at the interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional micro LED structures are used with uniform refractive indices, then the device structure is simple, but light extraction efficiency is low due to high reflection at interfaces
Solution Approach 1:
The patent changes the refractive index parameter of the n-type III-nitride layer by incorporating aluminum to create a gradient refractive index distribution. This parameter change reduces the refractive index difference at interfaces, thereby reducing reflection and improving light extraction efficiency without significantly complicating the device structure
Solution Approach 2:
The patent uses composite material design by combining n-type III-nitride layers with different aluminum compositions to form a gradient structure. This composite approach allows optimization of optical properties while maintaining structural integrity and manufacturability
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 effectively improves light extraction efficiency by allowing more light to be transmitted from the first n-type III-nitride layer into the second n-type III-nitride layer, resulting in better performance and flexibility in manufacturing processes.
Implementation Method 1
A refractive index of the second n-type III-nitride layer is smaller than a refractive index of the first n-type III-nitride layer and varies in a monotonically non-decreasing manner from the top surface. The refractive index of the second n-type III-nitride layer is larger at the bottom surface than at the top surface.
Implementation Method 2
Existing micro light-emitting diode (LED) devices face challenges in achieving efficient light extraction due to significant differences in refractive indices between layers, leading to high reflection and reduced efficiency.
Data Source
AI summary
A micro light-emitting diode device includes a substrate, a micro light-emitting diode, and a cathode transparent electrode. The micro light-emitting diode is disposed on the substrate and includes a p-type III-nitride layer, a first n-type III-nitride layer above the p-type III-nitride layer, a second n-type III-nitride layer above the first n-type III-nitride layer, and an active layer between the p-type and first n-type III-nitride layers. The second n-type III-nitride layer contains aluminum and has top and bottom surfaces. A refractive index of the second n-type III-nitride layer is smaller than a refractive index of the first n-type III-nitride layer and varies in a monotonically non-decreasing manner from the top surface. The refractive index of the second n-type III-nitride layer is larger at the bottom surface than at the top surface. The cathode transparent electrode is in contact with the top surface.