III-Nitride Crystal Composite on Laterally Stacked Substrates
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Solution Overview
Problem
Existing methods for manufacturing Group-III nitride crystals with non-{0001} plane orientations face challenges in achieving superior crystallinity due to thermal expansion disparities and non-selective growth on silicon oxide films, leading to reduced light-emission efficiency in semiconductor devices.
Innovation Solution
A method involving slicing III-nitride bulk crystal substrates with specific plane orientations and growing epitaxial III-nitride crystals on them, ensuring parallel alignment and similar thermal expansion coefficients to minimize strain, and using substrates with misoriented surfaces by up to 5° to stabilize crystal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If crystal masses are embedded into sapphire substrate for growing GaN crystal, then GaN crystal with non-{0001} plane orientation can be obtained, but thermal expansion disparity causes fractures and strains reducing crystallinity
Solution Approach 1:
The patent uses GaN crystal slices as substrates instead of sapphire substrates. Since GaN slices have the same thermal expansion coefficient and crystal structure as the grown GaN crystal, they provide a homogeneous foundation that eliminates thermal expansion mismatch and reduces fractures and strains during crystal growth, thereby maintaining superior crystallinity while enabling non-{0001} plane orientation control.
Solution Approach 2:
The patent changes the substrate material parameter from sapphire to GaN crystal slices. This parameter change fundamentally alters the thermal expansion properties of the substrate system, matching the thermal expansion coefficient between substrate and epitaxial layer, thus preventing the formation of fractures and strains that would otherwise occur due to thermal expansion disparity.
2Productivity
If AlxGayIn1-x-yN is grown on silicon oxide film, then crystal growth occurs, but non-selective growth on silicon oxide reduces crystallinity
Solution Approach 1:
The patent employs GaN crystal slices with specific non-{0001} plane orientations as substrates. These substrates provide locally optimized crystal structures that promote selective and uniform growth of AlxGayIn1-x-yN only on the desired crystal planes. The specific orientation of the GaN slice substrates ensures that the epitaxial growth occurs with high crystallinity by matching the crystallographic orientation, preventing non-selective growth on silicon oxide films.
3Ease of manufacture
If III-nitride crystal is grown on {0001} plane substrate, then manufacturing is simplified, but spontaneous polarization reduces light-emission efficiency
Solution Approach 1:
The patent deliberately uses GaN crystal slices with non-{0001} plane orientations (such as {10-10}, {11-20}, or {20-21} planes) as substrates. This asymmetric choice of substrate orientation fundamentally changes the crystal growth direction and reduces or eliminates spontaneous polarization effects in the grown III-nitride crystal. While this approach requires more complex substrate selection and preparation compared to standard {0001} substrates, it significantly improves light-emission efficiency by minimizing polarization-induced efficiency losses in light-emitting devices.
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 production of III-nitride crystals with superior crystallinity and improved light-emission efficiency by reducing dislocation density and enhancing uniformity across the crystal surface, leading to higher performance in semiconductor devices.
Implementation Method 1
a III-nitride crystal epitaxially present on the plurality of bulk III-nitride crystal slices
Data Source
AI summary
Group-III nitride crystal composites made up of especially processed crystal slices, cut from III-nitride bulk crystal, whose major surfaces are of {1-10±2}, {11-2±2}, {20-2±1} or {22-4±1} orientation, disposed adjoining each other sideways with the major-surface side of each slice facing up, and III-nitride crystal epitaxially present on the major surfaces of the adjoining slices, with the III-nitride crystal containing, as principal impurities, either silicon atoms or oxygen atoms.