Corundum Orientation Layer for Low-Defect GaN and α-Ga2O3 Growth
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Solution Overview
Problem
Current methods for reducing crystal defects in semiconductor devices, such as those using gallium nitride (GaN) and α-gallium oxide (α-Ga2O3), are insufficient for achieving high dielectric breakdown electric field characteristics, particularly due to lattice mismatch issues during heteroepitaxial growth on sapphire substrates.
Innovation Solution
A base substrate with an orientation layer having a corundum-type crystal structure with an a-axis length and/or c-axis length larger than sapphire, composed of materials like α-Cr2O3, α-Fe2O3, or α-Ti2O3, or their solid solutions, is used for crystal growth, reducing lattice mismatch and crystal defects by controlling the lattice constant and incorporating a gradient composition region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heteroepitaxial growth is performed on a sapphire substrate, then semiconductor layers can be formed, but crystal defects occur due to lattice mismatch between sapphire and the semiconductor materials
Solution Approach 1:
The patent introduces an orientation layer composed of corundum-type oxide (such as α-Al2O3, α-Cr2O3, α-Fe2O3, α-Ti2O3, or their solid solutions) as an intermediary between the sapphire substrate and the semiconductor layer. This orientation layer has a lattice constant closer to that of the semiconductor material (GaN or α-Ga2O3) than sapphire does, thereby reducing lattice mismatch and minimizing crystal defects during heteroepitaxial growth
Solution Approach 2:
The patent changes the lattice constant parameter of the substrate system by selecting corundum-type oxides with specific lattice constants that intermediate between sapphire and the target semiconductor material. By adjusting the composition (e.g., solid solution ratios of α-Al2O3 and α-Cr2O3), the lattice constant can be optimized to reduce mismatch with the semiconductor layer
2Reliability
If a buffer layer is introduced to reduce lattice mismatch, then crystal defects are reduced, but the dielectric breakdown electric field characteristics are still insufficient for power semiconductor applications
Solution Approach 1:
The patent optimizes the composition and structure of the orientation layer to achieve a lattice constant that closely matches the semiconductor material. By carefully selecting the corundum-type oxide composition (e.g., specific solid solution ratios), the lattice mismatch is minimized to below 1%, dramatically reducing crystal defect density to levels suitable for high-power semiconductor applications
Solution Approach 2:
The patent employs composite corundum-type oxide materials, including solid solutions of multiple corundum phases (e.g., α-Al2O3-α-Cr2O3, α-Al2O3-α-Fe2O3, or α-Al2O3-α-Ti2O3), to achieve optimal lattice constant matching while maintaining structural stability and low defect density
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 and improves the quality of semiconductor layers, achieving lower X-ray rocking curve half widths and higher dielectric breakdown electric field characteristics, suitable for power semiconductor applications.
Implementation Method 1
the a-axis length (4.754 Å) of sapphire (α-Al2O3) and the a-axis length (4.983 Å) of α-Ga2O3 differ by about 4.8%, and this difference is the main cause of crystal defects
Implementation Method 2
a half width of an X-ray rocking curve of a (104) plane of the corundum-type crystal structure on the front surface is 500 arcsec. or less
Data Source
AI summary
Provided is a base substrate including an orientation layer used for crystal growth of a nitride or oxide of a Group 13 element, in which a front surface on a side used for the crystal growth of the orientation layer is composed of a material having a corundum-type crystal structure having an a-axis length and/or c-axis length larger than that of sapphire, the orientation layer contains a material selected from the group consisting of α-Cr2O3, α-Fe2O3, α-Ti2O3, α-V2O3, and α-Rh2O3, or a solid solution containing two or more selected from the group consisting of α-Al2O3, α-Cr2O3, α-Fe2O3, α-Ti2O3, α-V2O3, and α-Rh2O3, and a half width of an X-ray rocking curve of a (104) plane of the corundum-type crystal structure is 500 arcsec. or less.