GaN LED Emission Pattern Layer for Light Extraction
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Solution Overview
Problem
The existing manufacturing methods for GaN-based LEDs on sapphire substrates face challenges such as reduced light-emitting efficiency, increased manufacturing costs, and difficulty in large-area growth due to lattice constant and thermal expansion coefficient mismatches, as well as light output reduction during the laser lift-off process.
Innovation Solution
The use of a silicon substrate for GaN LED manufacturing, which includes forming a buffer layer with alternating AlN and AlGaN layers, and an uneven emission pattern layer with AlN and AlGaN layers, along with a metal layer for light reflection and insulating layers for contact, to enhance light extraction efficiency and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaN-based compound semiconductor is grown on a sapphire substrate in the form of a thin film, then the LED can be manufactured, but light emitting efficiency is reduced due to lattice constant mismatch and thermal expansion coefficient difference
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the sapphire substrate and the GaN-based light-emitting layer. This buffer layer serves as a transition zone that compensates for the lattice constant mismatch and thermal expansion coefficient difference, thereby improving light emitting efficiency while enabling successful manufacturing on sapphire substrates
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers including the sapphire substrate, buffer layer, and GaN-based light-emitting layer. This composite material approach allows each layer to fulfill its specific function while collectively resolving the incompatibility between sapphire substrate and GaN film
2Productivity
If a GaN thin film is grown on a sapphire substrate, then LED manufacturing is possible, but large area growth is difficult and manufacturing costs increase
Solution Approach 1:
The buffer layer acts as a mediator that enables large-area growth of GaN films on sapphire substrates by providing a stable intermediate interface that reduces defects and facilitates uniform film formation across larger areas, thereby improving productivity without significantly increasing manufacturing costs
3Ease of manufacture
If a laser lift-off process is performed to remove a sapphire substrate after growing a GaN thin film, then substrate removal is achieved, but the output of light is reduced due to laser impact
Solution Approach 1:
The patent extracts or removes the sapphire substrate from the final LED structure through the laser lift-off process, separating the functional GaN-based light-emitting layer from the non-functional sapphire substrate. This extraction enables the use of cost-effective sapphire substrates during manufacturing while eliminating them from the final product that affects light output
Solution Approach 2:
The laser lift-off process is performed as a preliminary action before final LED assembly, removing the sapphire substrate before the light-emitting layer is fully integrated into the final device structure, thereby minimizing the impact of laser processing on the final light output performance
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 approach increases light extraction efficiency and reduces manufacturing costs by minimizing substrate warping and eliminating the need for laser lift-off, resulting in improved LED performance and production efficiency.
Implementation Method 1
an emission pattern layer on the first semiconductor layer, the emission pattern layer including a plurality of layers and having an emission pattern that externally emits light generated from the active layer
Implementation Method 2
a metal layer under the second semiconductor layer and configured to reflect light generated from the active layer toward the emission pattern layer
Data Source
AI summary
Example embodiments are directed to light-emitting devices (LEDs) and methods of manufacturing the same. The LED includes a first semiconductor layer; a second semiconductor layer; an active layer formed between the first and second semiconductor layers; and an emission pattern layer including a plurality of layers on the first semiconductor layer, the emission pattern including an emission pattern for externally emitting light generated from the active layer.