Nitride Semiconductor Crystallinity via Dual-Shape Sapphire Projections
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Solution Overview
Problem
Conventional methods for growing nitride semiconductors on sapphire substrates with projections suffer from deteriorated crystallinity and abnormal growth, leading to poor light extraction efficiency due to mismatched projection shapes and lattice mismatch, resulting in dislocations and voids.
Innovation Solution
A method involving dry etching to form circular bottom surfaces on sapphire substrates with triangular pyramid-shaped projections, which suppresses abnormal crystal growth and promotes vertical and lateral growth of nitride semiconductors, improving crystallinity and light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If projections with substantially triangle shape bottom surface are formed on sapphire substrate, then light extraction efficiency is improved, but crystallinity deteriorates and abnormal growth occurs
Solution Approach 1:
The projection is designed with different shapes at different locations: the bottom surface has a substantially triangular shape to improve light extraction, while the top surface has a substantially hexagonal shape to promote proper crystal growth. This local differentiation allows each region to serve its specific function without compromising overall performance.
Solution Approach 2:
The sapphire substrate is pre-formed with projections having the optimized dual-shape structure before nitride semiconductor crystal growth. This preliminary preparation ensures that the crystal growth process occurs on a pre-optimized surface geometry that promotes both light extraction and crystallinity.
2Illumination intensity
If projections are formed on sapphire substrate to improve light extraction, then light extraction efficiency increases, but abnormal crystal growth from projection portions occurs
Solution Approach 1:
The projection geometry is optimized with a substantially hexagonal top surface that matches the crystal structure of nitride semiconductors, ensuring uniform and reliable crystal growth while maintaining the triangular bottom surface for light extraction enhancement.
3Ease of manufacture
If conventional projection shapes are used, then manufacturing is simpler, but etching precision and growth control are insufficient
Solution Approach 1:
The projection geometry is precisely controlled with specific parameters: the bottom surface has a substantially triangular shape while the top surface has a substantially hexagonal shape. This parameter optimization achieves both manufacturing feasibility and high etching precision for better crystal growth control.
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 method enhances the crystallinity and light emission efficiency of nitride semiconductor elements by forming circular bottom surfaces and triangular pyramid-shaped projections, reducing dislocations and voids, and ensuring uniform hole dimensions for consistent crystal growth.
Implementation Method 1
dry etching a main surface of a sapphire substrate at a c-plane side
Implementation Method 2
wet etching the sapphire substrate to form an upper part of the projection into a triangular pyramid shape
Implementation Method 3
growing a semiconductor layer made of a nitride semiconductor on a dry etched surface and a wet etched surface
Data Source
AI summary
A method of manufacturing a nitride semiconductor element includes dry etching a main surface of a sapphire substrate at a c-plane side thereof, using a mask provided on the main surface, to form a plurality of projections, each having a circular bottom surface; wet etching the sapphire substrate to form an upper part of each projection into a triangular pyramid shape while maintaining the circular bottom surface of the projection; and growing a semiconductor layer made of a nitride semiconductor on a dry etched surface and a wet etched surface of the sapphire substrate.