GaN Light Emitting Device Ga-Substrate Growth
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Solution Overview
Problem
The existing methods for manufacturing light emitting devices using sapphire substrates face issues due to lattice misalignment, electrical non-conductivity, and low thermal conductivity, which degrade device characteristics, particularly when gallium nitride thin films are grown on these substrates.
Innovation Solution
A method involving the formation of a first-conductivity-type semiconductor layer on a substrate, followed by the use of multiple substrates and bonding layers to separate and couple the layers effectively, including the use of buffer layers, bonding layers, and etching techniques to enhance semiconductor growth and reduce lattice misalignment, while using substrates like sapphire, GaN, and SiC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a GaN thin film is grown on a sapphire substrate, then the device can be manufactured using commercially available substrates, but lattice misalignment causes dislocation propagation into the GaN thin film, degrading device characteristics
Solution Approach 1:
The patent introduces an AlN buffer layer as an intermediary between the sapphire substrate and the GaN active layer. This buffer layer serves as a mediator that reduces lattice misalignment and prevents dislocation propagation from the sapphire substrate to the GaN thin film, thereby maintaining device characteristics while still using commercially available sapphire substrates
Solution Approach 2:
The patent segments the semiconductor structure into distinct layers with different functions: the sapphire substrate provides mechanical support, the AlN buffer layer handles lattice mismatch and dislocation management, and the GaN active layer performs the light-emitting function. This segmentation allows each layer to optimize its specific role while mitigating the drawbacks of using sapphire substrates
2Ease of manufacture
If a sapphire substrate is used for growing GaN thin films, then manufacturing can proceed with available materials, but the electrical non-conductivity and low thermal conductivity of sapphire degrade the semiconductor layer performance
Solution Approach 1:
The AlN buffer layer acts as an intermediary that electrically and thermally couples the electrically insulating sapphire substrate to the semiconductor layers. This buffer layer provides a transition zone that improves electrical conductivity and thermal management for the GaN layers while allowing the use of sapphire substrates
Solution Approach 2:
The patent changes the material parameters at the substrate-interface by introducing AlN with different electrical and thermal properties compared to sapphire. This parameter change creates a gradient that improves electrical conductivity and thermal conductivity from the substrate interface toward the active layers, enhancing semiconductor layer quality
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 improves the growth and characteristics of semiconductor layers, reducing lattice misalignment and enhancing thermal conductivity, leading to improved performance and efficiency in light emitting devices.
Implementation Method 1
forming a bonding layer between the second surface and the second substrate
Implementation Method 2
The first substrate may be separated from the first-conductivity-type semiconductor layer, using at least one of a chemical-mechanical polishing method, an electrical-chemical etching method, and a wet etching method using a liquid etchant
Data Source
AI summary
A method for manufacturing a light emitting device is disclosed. The disclosed method includes forming a first-conductivity-type semiconductor layer over a first substrate such that a first surface of the first-conductivity-type semiconductor layer is adjacent to the first substrate, disposing a second substrate on a second surface of the first-conductivity-type semiconductor layer opposite the first surface, separating the first substrate, disposing a third substrate on the first surface, separating the second substrate, and forming an active layer and a second-conductivity-type semiconductor layer over the second surface. In accordance with the method, it is possible to use a relatively inexpensive substrate. As a semiconductor layer is formed over a Ga-face of a gallium nitride semiconductor layer, an increase in light emission efficiency is achieved.