Engineered Ceramic Substrate for Uniform GaN Epitaxy
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Solution Overview
Problem
The heteroepitaxial growth of gallium nitride based LED structures on sapphire substrates leads to reduced uniformity and adverse effects on the electronic/optical properties of the epitaxial layers, necessitating improved methods and systems for epitaxial growth processes and substrate structures.
Innovation Solution
The development of an engineered substrate structure with a coefficient of thermal expansion (CTE) matched to epitaxial layers, comprising a polycrystalline ceramic core, adhesion layers, a conductive layer, and a barrier layer, which simplifies process integration and enhances the match with gallium nitride-based epitaxial and device layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heteroepitaxial growth is used to grow gallium nitride LED structures on sapphire substrates, then the substrate can support epitaxial growth, but the uniformity and electronic/optical properties of the epitaxial layers are reduced
Solution Approach 1:
The patent introduces an intermediary layer structure between the sapphire substrate and the gallium nitride epitaxial layers. This intermediate structure acts as a mediator that improves the interface quality and reduces adverse effects on the epitaxial growth, thereby improving uniformity and electronic/optical properties while still supporting the growth process
Solution Approach 2:
The patent employs a composite substrate structure consisting of multiple materials including sapphire, silicon oxide, and silicon layers. This composite structure combines the advantages of different materials to provide both mechanical support and improved epitaxial growth conditions, resolving the contradiction between supporting growth and maintaining layer quality
2Device complexity
If heteroepitaxial growth is used on sapphire substrates, then the substrate structure is simple, but adverse effects on electronic and optical properties occur
Solution Approach 1:
The patent segments the substrate structure into distinct functional layers including a sapphire substrate, silicon oxide layer, and silicon layer. This segmentation allows each layer to perform its specific function optimally, improving electronic and optical properties while keeping the overall structure manageable and not excessively complex
3Ease of manufacture
If conventional substrate structures are used, then process integration is straightforward, but impurity diffusion occurs and uniformity is reduced
Solution Approach 1:
The patent introduces barrier layers as intermediary elements that prevent impurity diffusion from the substrate into the epitaxial layers. These intermediary barrier layers maintain process integration feasibility while significantly improving the uniformity and quality of the grown layers by blocking harmful diffusion paths
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
The engineered substrate structure improves the uniformity and electronic/optical properties of epitaxial layers, prevents impurity diffusion, and simplifies process integration, making it suitable for optical, electronic, and optoelectronic applications.
Implementation Method 1
a first adhesion layer coupled to the polycrystalline ceramic core; a second adhesion layer coupled to the conductive layer; a barrier layer coupled to the second adhesion layer
Implementation Method 2
a substrate structure suitable for epitaxial growth that is characterized by a coefficient of thermal expansion (CTE) that is substantially matched to epitaxial layers grown thereon
Implementation Method 3
forming an epitaxial silicon layer by epitaxial growth on the substantially single crystalline silicon layer, and forming an epitaxial III-V layer by epitaxial growth on the epitaxial silicon layer
Data Source
AI summary
A substrate includes a support structure comprising a polycrystalline ceramic core, a first adhesion layer encapsulating the polycrystalline ceramic core, a barrier layer encapsulating the first adhesion layer, a second adhesion layer coupled to the barrier layer, and a conductive layer coupled to the second adhesion layer. The substrate also includes a bonding layer coupled to the support structure, a substantially single crystal silicon layer coupled to the bonding layer, and an epitaxial semiconductor layer coupled to the substantially single crystal silicon layer.