Gallium Nitride Substrate with Random Intermediate Layer
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Solution Overview
Problem
Existing methods for growing gallium nitride crystals, such as vapor phase growth, result in a high number of crystal defects due to lattice mismatching and require complex and costly facilities, while liquid phase growth methods still struggle to sufficiently reduce defects.
Innovation Solution
A semiconductor substrate with a sapphire substrate, an intermediate layer of gallium nitride with random crystal directions, and semiconductor layers of gallium nitride single crystals, where the gallium nitride layers contain iron atoms with controlled concentration distributions, are used. The gallium nitride layers are grown using a liquid phase method involving heating metal gallium and iron nitride in a nitrogen atmosphere, with a reaction temperature between 700°C and 1000°C, and a holding time of at least 20 hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vapor phase growth method is used to form gallium nitride on sapphire substrate, then gallium nitride crystal can be grown, but a large number of crystal defects occur due to lattice mismatching and thermal expansion coefficient difference
Solution Approach 1:
The patent introduces an intermediate layer between the sapphire substrate and the gallium nitride crystal. This intermediate layer acts as a mediator that gradually transitions from the sapphire substrate lattice structure to the gallium nitride lattice structure, reducing the abrupt lattice mismatching and thermal expansion coefficient difference. This allows the gallium nitride crystal to grow with fewer defects and better structural integrity.
Solution Approach 2:
The patent employs liquid phase growth method with controlled temperature parameters (heating to specific temperatures and holding for extended periods) to grow gallium nitride crystals. By carefully controlling the growth temperature and duration, the method achieves superior crystal quality with reduced defects compared to conventional vapor phase growth, while also simplifying the production process.
2Manufacturing precision
If vapor phase growth method is used with ammonia gas as nitrogen source, then gallium nitride crystal can be synthesized, but production process and apparatus become complicated and production cost increases
Solution Approach 1:
The patent changes the growth method from vapor phase to liquid phase growth, fundamentally altering the process parameters. This substitution eliminates the need for complex ammonia gas handling systems and high-reactivity gas flow control apparatus. The liquid phase method uses simpler heating and holding processes, reducing both apparatus complexity and production costs while maintaining crystal synthesis capability.
3Manufacturing precision
If liquid phase growth method is used to grow gallium nitride crystal, then crystal defects are reduced compared to vapor phase growth, but it remains difficult to form gallium nitride crystal with sufficiently reduced crystal defects
Solution Approach 1:
The patent applies preliminary action by first forming an intermediate layer on the sapphire substrate before growing the gallium nitride crystal. This intermediate layer prepares the substrate surface with appropriate lattice matching characteristics, creating a favorable foundation for subsequent crystal growth. This preliminary step significantly reduces the nucleation of defects and enables the formation of high-quality gallium nitride crystals with sufficient defect reduction to achieve target characteristics.
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 significantly reduces crystal defects in gallium nitride crystals, improving their crystallinity and reducing production costs by using a simpler growth method with fewer environmental hazards.
Implementation Method 1
heating metal gallium and iron nitride in a nitrogen atmosphere to at least a reaction temperature at which the iron nitride and the metal gallium react together
Implementation Method 2
a gallium nitride crystal can be grown in a layer form in a staircase configuration by crystal precipitation from a liquid phase
Implementation Method 3
heating metal gallium and iron nitride in a nitrogen atmosphere to at least a reaction temperature
Implementation Method 4
crystal precipitation from a liquid phase
Data Source
AI summary
There is provided a semiconductor substrate including: a sapphire substrate; an intermediate layer formed of gallium nitride with random crystal directions and provided on the sapphire substrate; and at least one or more semiconductor layers each of which is formed of a gallium nitride single crystal and that are provided on the intermediate layer.