Group 13 Nitride Crystal Layer with M-Plane Orientation
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Solution Overview
Problem
Existing gallium nitride crystal-based light-emitting devices face issues with dislocation density and luminance efficiency, particularly as device size increases, due to anisotropic grain orientations and void formation during crystal growth.
Innovation Solution
A microstructure is developed for a group 13 nitride crystal layer with a linear high-luminance light-emitting part extending along the m-plane and a low-luminance region, where the upper surface has an off-angle of 2.0° or less, reducing dislocation density and property deviations, and a free-standing substrate is created with this layer for improved epitaxial growth and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device size is increased, then the productivity is improved, but voids are left on the peripheral part of the crystal due to difficulty in controlling melt flow
Solution Approach 1:
The patent applies parameter changes by controlling the rotation speed of the crucible during crystal growth. By optimizing rotation speed parameters, the melt flow is evenly distributed across the substrate surface, preventing void formation even when producing large-sized 6-inch or larger semiconductor crystals. This parameter optimization enables both high productivity through larger device sizes and high manufacturing precision by eliminating peripheral voids.
2Reliability
If the grain size is increased to reduce dislocation density, then the reliability is improved, but anisotropic property of orientations causes current path interruption and luminance efficiency reduction
Solution Approach 1:
The patent applies asymmetry by intentionally creating a controlled tilt angle (off-angle) of the crystal orientation relative to the substrate normal. This asymmetric orientation control, specifically setting the off-angle within 1° to 10°, prevents anisotropic grain alignment that would cause current path interruption. The controlled asymmetric orientation enables large grain sizes for low dislocation density while maintaining uniform electrical properties and high luminance efficiency.
Solution Approach 2:
The patent uses parameter changes by optimizing the off-angle parameter of crystal orientation. By controlling this angular parameter within a specific range (1° to 10°), the patent achieves both low dislocation density through adequate grain size and prevents anisotropic effects that reduce luminance efficiency. This parameter optimization simultaneously improves reliability and eliminates harmful anisotropic properties.
3Reliability
If a high Ga ratio is applied to reduce dislocation density, then the reliability is improved, but voids tend to be present between the grains
Solution Approach 1:
The patent applies parameter changes by optimizing multiple parameters simultaneously: the rotation speed of the crucible and the off-angle of crystal orientation. By coordinating these parameter changes, the patent achieves low dislocation density through controlled grain growth while preventing void formation between grains through even melt distribution. This multi-parameter optimization resolves the contradiction between reliability improvement and void prevention.
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 microstructure achieves lower dislocation density and uniform properties, enhancing the yield and performance of functional devices by suppressing growth deviations and void formation, even at larger sizes, such as 6 inches or larger.
Implementation Method 1
said upper surface being observed by cathode luminescence
Data Source
AI summary
A layer of a crystal of a group 13 nitride selected from gallium nitride, aluminum nitride, indium nitride and the mixed crystals thereof has an upper surface and a bottom surface. The upper surface includes a linear high-luminance light-emitting part and a low-luminance light-emitting region adjacent to the high-luminance light-emitting part. The high-luminance light-emitting part includes a portion extending along an m-plane of the crystal of the group 13 nitride. A normal line to the upper surface has an off-angle of 2.0° or less with respect to <0001> direction of the crystal of the nitride of the group 13 element.