III-Nitride Crystal Substrates for Fracture-Free Growth
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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 fractures and compromised crystallinity.
Innovation Solution
The method involves slicing Group-III nitride bulk crystals into substrates with specific plane orientations, aligning them for uniform growth, and using these substrates to grow epitaxial crystals with {h0k0i0l0} orientations, ensuring thermal compatibility and uniform chemical composition to prevent fractures and enhance crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If crystal masses are embedded into sapphire substrate for vapor deposition growth, then non-{0001} plane orientation crystals can be grown, but thermal expansion disparity causes fractures and strains reducing crystallinity
Solution Approach 1:
The patent uses GaN substrates with the same material composition as the grown crystal, ensuring homogeneous thermal expansion properties throughout the structure. This eliminates the thermal expansion mismatch between sapphire substrate and GaN crystal that causes fractures and strains, while still enabling controlled growth of crystals with non-{0001} plane orientations.
Solution Approach 2:
The patent changes the substrate material parameter from sapphire to GaN, which has matching thermal expansion characteristics. This parameter change resolves the thermal compatibility issue while maintaining the ability to control crystal plane orientation through appropriate substrate preparation and growth conditions.
2Productivity
If AlxGayIn1-x-yN is grown on silicon oxide film, then crystal growth occurs, but non-selective growth on the film reduces crystallinity
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the substrate and the AlxGayIn1-x-yN crystal growth. This buffer layer provides a selective nucleation surface that promotes epitaxial growth only on desired sites, preventing non-selective growth on the silicon oxide film while maintaining high growth rates and superior crystallinity.
Solution Approach 2:
The patent applies local quality by creating specific surface conditions only in certain regions through the buffer layer, enabling selective growth on the buffer layer while preventing growth on the silicon oxide film. This localized control of growth properties achieves both high productivity and superior crystallinity.
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 results in Group-III nitride crystals with superior crystallinity, characterized by narrow x-ray diffraction peaks and reduced threading dislocation density, improving light-emission efficiency in semiconductor devices.
Implementation Method 1
by means of a vapor-phase technique such as hydride vapor-phase epitaxy (HVPE) or metalorganic chemical vapor deposition (MOCVD)
Implementation Method 2
with x-ray diffraction full-width-at-half-maximums (FWHMs) being measured along an axis defined by a <100> direction of the substrate projected onto either of the major surfaces
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. With x-ray diffraction FWHMs being measured along an axis defined by a <0001> direction of the substrate projected onto either of the major surfaces, FWHM peak regions are present at intervals of 3 to 5 mm width. Also, with threading dislocation density being measured along a <0001> direction of the III-nitride crystal substrate, threading-dislocation-density peak regions are present at the 3 to 5 mm intervals.