LED Epitaxial Structure Textured Low-Temperature Layer
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Solution Overview
Problem
Conventional LED epitaxial structures on sapphire substrates suffer from reduced light emission efficiency due to threading dislocations and inefficient heat dissipation, leading to saturation in light output.
Innovation Solution
The proposed LED epitaxial structure features a textured low-temperature epitaxial layer with cavities filled by a SiO2 layer and a high-temperature epitaxial layer, along with an optional AlN laminated film, to enhance light extraction efficiency by reducing total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a sapphire substrate is used for LED epitaxial growth, then the structural stability and chemical inertness are improved, but the heat dissipation efficiency deteriorates and light extraction efficiency is reduced due to total internal reflection
Solution Approach 1:
The patent segments the epitaxial structure into multiple functional layers with different temperatures and compositions. The low-temperature epitaxial layer is divided into first and second portions with different AlGaN compositions, creating a segmented structure that addresses both heat dissipation and light extraction issues while maintaining the benefits of the sapphire substrate
Solution Approach 2:
The patent applies local quality by creating regions with different AlGaN compositions within the low-temperature epitaxial layer. The first portion has a different composition than the second portion, allowing each region to optimize for specific functions such as heat dissipation or light extraction in different local areas of the device
2Ease of manufacture
If conventional epitaxial layers are used, then the manufacturing process is simple, but threading dislocations degrade the LED performance and light emission efficiency
Solution Approach 1:
The patent performs preliminary action by growing a low-temperature epitaxial layer with specific composition gradients before forming the high-temperature layers. This preliminary layer is designed to reduce threading dislocations that would otherwise propagate through the entire structure, preventing reliability issues before they affect the final device performance
Solution Approach 2:
The patent uses composite materials by combining AlGaN layers with different aluminum compositions and temperatures. The low-temperature AlGaN layer with graded composition is combined with high-temperature AlGaN layers to create a composite structure that reduces dislocations while maintaining manufacturing feasibility
3Illumination intensity
If the light emission intensity is increased by increasing input power, then the brightness is improved, but the light emission efficiency saturates due to heat accumulation and total internal reflection
Solution Approach 1:
The patent addresses the saturation issue by introducing dimensional changes through the textured surface structure on the upper surface of the low-temperature epitaxial layer. This creates additional light extraction pathways in different dimensions and angles, reducing total internal reflection and allowing continued improvement in light emission efficiency as input power increases
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 increases light extraction efficiency by reflecting and transmitting light more effectively, overcoming the limitations of conventional structures and improving overall output.
Implementation Method 1
the light emission from electroluminescent devices or from LEDs is limited by the total internal reflection occurring at the surface between the semiconductor substrate wherein the device is fabricated and the surrounding medium
Data Source
AI summary
An LED epitaxial structure includes a substrate, a buffer layer, a functional layer and a light generating layer. The buffer layer is located on a top surface of the substrate. The functional layer includes a plurality of high-temperature epitaxial layers and low-temperature epitaxial layers alternatively arranged between the buffer layer and light generating layer. A textured structure is formed in the low-temperature epitaxial layer. A SiO2 layer including a plurality of convexes is located on the textured structure to increase light extraction efficiency of the LED epitaxial structure. A manufacturing method of the LED epitaxial structure is also disclosed.