Group III Nitride Semiconductor Multilayer Structure With Grooved Substrate
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Solution Overview
Problem
The challenge lies in growing high-quality Group III nitride semiconductor single crystals on substrates like sapphire or silicon carbide, which have significant lattice mismatches, leading to difficulties in achieving good crystallinity and requiring costly surface smoothing processes.
Innovation Solution
A Group III nitride semiconductor multilayer structure is developed using a substrate with non-periodically distributed grooves of specific depths, combined with a buffer layer and single-crystal layer grown via controlled nitrogen and Group III element source feeding, allowing for horizontal growth and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low-temperature buffer layer is deposited onto a substrate followed by high-temperature epitaxial growth, then good crystallinity can be achieved, but the process complexity and production cost increase
Solution Approach 1:
The substrate surface is pre-treated with non-periodically distributed grooves before epitaxial growth. This preliminary action modifies the substrate surface morphology to promote horizontal growth of the Group III nitride semiconductor crystal, reducing the need for complex buffer layer processes while maintaining good crystallinity.
Solution Approach 2:
The invention changes the substrate surface parameters by introducing grooves with specific depth ranges (0.01 to 5 μm). This parameter modification affects the epitaxial growth behavior, enabling horizontal growth and reducing dislocation density without requiring complex multi-step buffer layer deposition.
2Manufacturing precision
If substrate surface smoothing is performed to achieve very low surface roughness, then excellent crystallinity can be obtained, but laborious processing steps and increased production cost are required
Solution Approach 1:
Non-periodically distributed grooves are introduced on the substrate surface as a preliminary action. These grooves serve as nucleation sites that guide the epitaxial growth, allowing the crystal to grow horizontally and self-smooth the surface without requiring laborious additional smoothing steps.
Solution Approach 2:
Instead of trying to eliminate surface irregularities through complex smoothing processes, the invention converts the substrate surface irregularities (grooves) into a beneficial feature. The grooves act as preferential nucleation sites that guide horizontal growth, transforming what would normally be harmful surface defects into useful growth templates.
3Ease of manufacture
If direct epitaxial growth is performed on a substrate with large lattice mismatch, then production cost is reduced, but good crystallinity cannot be achieved
Solution Approach 1:
The substrate surface is given non-uniform local quality through the introduction of non-periodically distributed grooves. These localized surface features create preferential nucleation sites that guide the epitaxial growth, allowing good crystallinity to be achieved directly on the substrate without requiring expensive buffer layers or complex intermediate structures.
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 enables the formation of Group III nitride semiconductors with excellent crystallinity and smooth surfaces without intricate substrate smoothing, simplifying the processing and reducing costs.
Implementation Method 1
there has generally been carried out a method disclosed in Japanese Patent No. 3026087 or Japanese Patent Application Laid-Open (kokai) No. 4-297023, in which a low-temperature buffer layer formed of aluminum nitride (AlN) or AlGaN is deposited onto a substrate, and a Group III nitride semiconductor crystal is epitaxially grown on the buffer layer at high temperature
Implementation Method 2
a Group III nitride semiconductor crystal is epitaxially grown on the buffer layer at high temperature
Implementation Method 3
a Group III element source and a nitrogen source are fed onto a heated substrate such that the ratio of nitrogen to a Group III element becomes 1,000 or less, or merely a Group III element source (in the case where the nitrogen/Group III element ratio is zero) is fed onto the substrate, to thereby form a Group III nitride semiconductor
Implementation Method 4
at the hetero-junction interface between aluminum gallium nitride (AlGaN) and gallium nitride (GaN), a two-dimensional electron layer is generated due to the piezoelectric effect
Data Source
AI summary
An object of the present invention is to provide a Group III nitride semiconductor multilayer structure having a smooth surface and exhibiting excellent crystallinity, which multilayer structure employs a low-cost substrate that can be easily processed. Another object is to provide a Group III nitride semiconductor light-emitting device comprising the multilayer structure.The inventive Group III nitride semiconductor multilayer structure comprises a substrate; an AlxGa1-xN (0≦x≦1) buffer layer which is provided on the substrate and has a columnar or island-like crystal structure; and an AlxInyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1) single-crystal layer provided on the buffer layer, wherein the substrate has, on its surface, non-periodically distributed grooves having an average depth of 0.01 to 5 μm.