Nitride Semiconductor Element With Angled Projections
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Solution Overview
Problem
Conventional nitride semiconductor LEDs grown on sapphire substrates with elongated trenches face issues with crystallinity deterioration due to mismatched timing of crystal growth between trench bottoms and surface, leading to poor temperature characteristics and high dislocation density.
Innovation Solution
A nitride semiconductor element is manufactured using a sapphire substrate with elongated projections angled between -10° to +10° relative to the a-plane, which reduces dislocation density and improves temperature characteristics by allowing lateral growth of the nitride semiconductor layer, thereby enhancing its thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If elongated trenches are provided at the sapphire substrate to reduce dislocation density, then dislocation density is reduced, but crystallinity deteriorates due to mismatched timing of crystal growth between trench bottom and surface
Solution Approach 1:
The patent inverts the conventional approach by replacing trenches (recess portions) with projections (convex portions). This inversion allows the nitride semiconductor layer to grow continuously from the projections without the crystallinity deterioration that occurs in trenches, while still achieving dislocation density reduction through the projection structure.
Solution Approach 2:
The patent introduces a specific angular orientation (10° to 70° relative to the c-plane) for the projections, adding an angular dimension to the structure. This angular configuration enables dislocation convergence and redirection, reducing dislocation density while maintaining crystallinity throughout the layer growth process.
2Ease of manufacture
If conventional sapphire substrate structure is used, then manufacturing is simple, but temperature characteristics are poor
Solution Approach 1:
The patent modifies the substrate surface geometry by introducing projections with specific angular orientations (10° to 70° relative to the c-plane). This parameter change in the substrate structure enables improved temperature characteristics through enhanced thermal management and reduced dislocation density, while remaining compatible with existing manufacturing processes.
3Stability of the object's composition
If crystal growth timing is synchronized between trench bottom and surface, then crystallinity is maintained, but dislocation density reduction effect is lost
Solution Approach 1:
By inverting trenches to projections, the patent eliminates the timing synchronization problem entirely. The projection structure naturally guides continuous crystal growth while maintaining crystallinity, and simultaneously achieves dislocation density reduction through the angular configuration that promotes dislocation convergence and redirection.
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 approach results in a nitride semiconductor layer with reduced dislocation density and improved temperature characteristics, as the angled projections facilitate the convergence of dislocations, leading to better thermal stability and light output consistency across varying temperatures.
Implementation Method 1
growing a nitride semiconductor layer on the surface of the sapphire substrate with the projections formed thereat
Data Source
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AI summary
A nitride semiconductor element includes a sapphire substrate including: a main surface extending in a c-plane of the sapphire substrate, and a plurality of projections disposed at the main surface, the plurality of projections including at least one projection having an elongated shape in a plan view; and a nitride semiconductor layer disposed on the main surface of the sapphire substrate. The at least one projection has an outer edge extending in a longitudinal direction of the elongated shape, the outer edge extending in a direction oriented at an angle in a range of -10° to +10° with respect to an a-plane of the sapphire substrate in the plan view.