Group III Nitride Substrate with Graded Mg Concentration
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Solution Overview
Problem
Group III nitride crystals grown on conventional substrates like sapphire or ScAlMgO4 often suffer from lattice mismatch issues, leading to crystal defects, warpage, and cracks, which deteriorate the quality of light emitting diodes and other devices.
Innovation Solution
A Group III nitride substrate with a base material having different Mg concentrations on its front and back surfaces is used, allowing for controlled lattice constant mismatch and the addition of Mg to enhance crystal quality, along with a buffer layer and a RAMgO4 substrate to reduce defects and improve mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sapphire substrate is used for growing Group III nitride crystal, then the substrate is readily available and easy to manufacture, but the lattice mismatch ratio is 13.8% leading to crystal defects
Solution Approach 1:
The patent changes the lattice constant parameter of the substrate by incorporating Mg into the ScAlMgO4 structure. By adjusting the Mg concentration, the lattice constant can be tuned to reduce the mismatch with Group III nitride crystal, thereby improving crystal quality while maintaining substrate availability
Solution Approach 2:
The patent uses a composite substrate structure consisting of ScAlMgO4 with controlled Mg concentration. This composite material combines the advantages of readily available sapphire-based substrates with improved lattice matching through Mg incorporation, resolving the contradiction between ease of manufacture and crystal quality
2Manufacturing precision
If an ScAlMgO4 substrate is used to reduce lattice mismatch, then the mismatch ratio is reduced compared to sapphire, but the lattice constant does not completely agree with Group III nitride causing warpage and cracks
Solution Approach 1:
The patent optimizes the Mg concentration parameter in ScAlMgO4 to achieve a lattice constant that better matches Group III nitride. By precisely controlling this parameter, the substrate reduces both lattice mismatch and thermal stress, preventing warpage and cracks while maintaining mechanical integrity
Solution Approach 2:
The patent incorporates Mg into the ScAlMgO4 substrate beforehand to create a lattice structure that anticipates and compensates for the mismatch with Group III nitride. This preliminary adjustment cushions against the development of warpage and cracks during crystal growth
3Manufacturing precision
If the Mg concentration is increased to improve lattice matching, then the lattice constant agreement improves, but the complexity of controlling uniform Mg distribution increases
Solution Approach 1:
The patent optimizes the Mg concentration parameter within a specific range (0.01 to 0.10 atomic ratio) to achieve good lattice matching without excessive complexity. This optimized parameter range balances lattice constant agreement with manageable manufacturing complexity
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 results in high-quality Group III nitride crystals with reduced lattice mismatch, minimizing crystal defects and enhancing the mechanical strength of the substrate, leading to improved performance in light emitting diodes and other electronic devices.
Implementation Method 1
the base material part and the third substrate have a small mismatch in lattice constant
Data Source
AI summary
A Group III nitride substrate contains a base material part of a Group III nitride having a front surface and a back surface, the front surface of the base material part and the back surface of the base material part having different Mg concentrations from each other.