GaN Epitaxial Structure with AlGaN Buffer for Lattice Mismatch
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Solution Overview
Problem
The use of third-generation semiconductor materials like gallium nitride for epitaxial structures faces challenges such as lattice mismatch, which affects the quality and performance of the semiconductor epitaxial structure.
Innovation Solution
A semiconductor epitaxial structure is proposed, comprising a substrate with an aluminum nitride layer, followed by a first and second aluminum gallium nitride layer, and a gallium nitride layer. The aluminum content in the first aluminum gallium nitride layer is higher than in the second, which helps reduce lattice mismatch and improve the epitaxial structure's quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gallium nitride is used for the semiconductor epitaxial structure, then high electron saturation velocity and high breakdown electric field are achieved, but lattice mismatch occurs between gallium nitride and silicon substrate
Solution Approach 1:
The patent introduces aluminum gallium nitride layers as intermediary buffer layers between the silicon substrate and the gallium nitride layer. These intermediate layers have lattice structures that gradually transition from the silicon substrate to the gallium nitride layer, acting as a mediator to reduce the lattice mismatch and dislocation density while allowing the high breakdown electric field properties of gallium nitride to be maintained.
Solution Approach 2:
The patent changes the compositional parameters of the buffer layers by using aluminum gallium nitride with varying aluminum and gallium contents. By adjusting the ratio of aluminum to gallium in the buffer layers, the lattice constant is gradually modified to bridge the mismatch between silicon and gallium nitride, thereby reducing dislocation density while preserving the electrical properties of the final gallium nitride layer.
2Temperature
If gallium nitride is used for the semiconductor epitaxial structure, then high thermal conductivity is achieved, but lattice mismatch and dislocation density affect the quality of the epitaxial structure
Solution Approach 1:
The aluminum gallium nitride buffer layers serve as intermediary structures that gradually transition the lattice parameters from the silicon substrate to the gallium nitride layer. This gradual transition reduces dislocation density and improves the quality of the epitaxial structure, allowing the high thermal conductivity properties of gallium nitride to be fully realized without being compromised by defects from direct growth on silicon.
3Ease of manufacture
If a single-layer structure is used, then the manufacturing process is simple, but lattice mismatch cannot be effectively reduced
Solution Approach 1:
The patent divides the buffer structure into multiple segmented layers of aluminum gallium nitride with different compositions, rather than using a single uniform layer. This segmentation allows each layer to progressively adjust the lattice parameters, effectively reducing lattice mismatch while maintaining a relatively straightforward manufacturing process that can be implemented using standard epitaxial growth techniques.
Data Source
AI summary
A semiconductor epitaxial structure, an application thereof and a manufacturing method therefor are provided. The semiconductor epitaxial structure includes a substrate, an aluminum nitride layer formed on the substrate, and a gallium nitride layer formed on the aluminum nitride layer. The semiconductor epitaxial structure can be applied in a semiconductor device and an electronic device.