Group III Nitride Semiconductor Growth on Asymmetric Posts
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Solution Overview
Problem
Existing methods for growing Group III nitride semiconductor crystals on concave-convex substrates face challenges such as deteriorated crystallinity and flatness due to void formation near side surfaces of trenches or posts, leading to high threading dislocation density and reduced external and internal quantum efficiency.
Innovation Solution
A method involving the formation of a concave-convex structure with specific stripe patterns on the substrate, where the first stripe structure is aligned parallel to the m-axis and the second stripe structure is aligned parallel to the a-axis, with carefully controlled angles between the processed side surfaces and the substrate's crystal planes to facilitate uniform threading dislocation density and lateral growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Group III nitride semiconductor is grown on a concave-convex sapphire substrate with trenches or posts, then light extraction performance is improved, but voids are formed near the side surfaces of the trenches or posts, resulting in deteriorated crystallinity and flatness
Solution Approach 1:
The patent applies asymmetry by orienting the side surfaces of trenches or posts at specific angles (0° to 10° relative to the a-plane) rather than symmetric vertical orientations. This asymmetric orientation controls the crystal growth direction of GaN, enabling it to preferentially grow toward the side surfaces and fill voids while maintaining the concave-convex structure for light extraction enhancement.
Solution Approach 2:
The patent changes the orientation parameter of the side surfaces from vertical (perpendicular to substrate) to inclined (0° to 10° relative to a-plane). This parameter change fundamentally alters the crystal growth behavior, allowing GaN to grow laterally along the side surfaces and eliminate void formation while preserving the light extraction benefits of the concave-convex structure.
2Manufacturing precision
If sides in planar view of trenches or posts intersect with an a-plane of a sapphire substrate, then GaN is difficult to grow on side surfaces and voids are avoided, but lateral growth of GaN is slow and surface flatness is deteriorated
Solution Approach 1:
The patent optimizes the orientation parameter of side surfaces to a specific range (0° to 10° relative to a-plane) that balances two competing requirements: maintaining crystallinity by intersecting with the a-plane and enabling sufficient lateral growth rate. This precise parameter control allows GaN to grow laterally at an acceptable rate while still avoiding void formation.
3Illumination intensity
If a second stripe structure is overlapped on a first stripe structure to improve light extraction, then external quantum efficiency is improved, but threading dislocations are locally distributed and internal quantum efficiency is reduced
Solution Approach 1:
The patent applies local quality by creating a grid pattern of trenches or posts with side surfaces oriented at specific angles (0° to 10° relative to a-plane). This local structural optimization ensures that GaN crystal growth is uniformly controlled at each location, preventing local accumulation of threading dislocations while maintaining the light extraction benefits of the multi-directional stripe structure.
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 semiconductors with improved crystal quality, reduced threading dislocation density, and enhanced light extraction performance by ensuring uniform threading dislocation distribution and efficient filling of spaces among facets, thereby improving the yield ratio of production.
Implementation Method 1
growing Group III nitride semiconductor in a c-axis direction of the Group III nitride semiconductor on the top surfaces of the posts and the bottom surfaces of the trenches
Data Source
AI summary
A first side surface of post of the first stripe is formed so that a plane which is most parallel to the first side surface among low-index planes of the growing Group III nitride semiconductor is a m-plane (10-10), and a first angle between the first lateral vector obtained by orthogonally projecting a normal vector of the first side surfaces to the main surface and a m-axis projected vector obtained by orthogonally projecting a normal vector of the m-plane of the growing semiconductor to the main surface is from 0.5° to 6°. A second side surface of post of the second stripe is formed so that a plane which is most parallel to the second side surface among low-index planes of the growing semiconductor is an a-plane (11-20), and a second angle between the second lateral vector and an a-axis projected vector of the a-plane is from 0° to 10°.