Light Emitting Device with Uneven Substrate Interface
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Solution Overview
Problem
Dislocations in semiconductor layers of light emitting devices due to lattice constant mismatch between substrates and nitride semiconductors lead to reduced crystallinity and efficiency, causing issues with current concentration and electrostatic discharge.
Innovation Solution
A light emitting device structure is developed with an uneven part, a discontinuous nonconductive layer, and a substrate layer to reduce dislocation density, featuring a layered structure that suppresses dislocations and improves crystallinity, comprising a first conductive type semiconductor layer, an active layer, and a second conductive type semiconductor layer, with the substrate layer having a lattice constant difference of 5% or lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a substrate with large lattice constant difference is used, then manufacturing is easier and cost is lower, but dislocation density increases and crystallinity deteriorates
Solution Approach 1:
The patent divides the interface between substrate and nitride semiconductor into multiple segments by forming an uneven surface with periodic convex and concave parts. This segmentation reduces the effective contact area and distributes dislocations, allowing use of substrates with larger lattice mismatch while maintaining crystallinity.
Solution Approach 2:
The patent applies local quality by creating regions with different surface properties - the convex parts provide contact areas while concave parts create dislocation barriers. This local variation in surface topology allows the structure to simultaneously achieve good crystallinity and compatibility with various substrates.
2Ease of manufacture
If a substrate with large lattice constant difference is used, then manufacturing is easier, but dislocation density increases and device reliability decreases
Solution Approach 1:
By segmenting the substrate interface into periodic convex and concave structures, the patent prevents dislocation propagation that would otherwise compromise device reliability. This segmentation allows use of cost-effective substrates while maintaining high reliability through reduced dislocation density.
Solution Approach 2:
The uneven surface structure acts as an intermediary between the substrate and the nitride semiconductor layer, mediating the lattice mismatch and preventing direct transmission of dislocations to the active device regions, thereby preserving reliability.
3Device complexity
If dislocation density is high, then manufacturing is simpler, but current concentration occurs and electrostatic discharge issues arise
Solution Approach 1:
The patent employs curved surface geometry with periodic convex parts that have specific curvature radii (5-50 μm). This curvature distributes electrical field lines and prevents current concentration at sharp edges, eliminating electrostatic discharge issues while maintaining structural simplicity.
Solution Approach 2:
By changing the geometric parameters of the uneven surface (convex part diameter, concave part depth, periodicity), the patent optimizes both dislocation management and electrical field distribution, preventing harmful current concentration without increasing overall device complexity.
Data Source
AI summary
A light emitting device is provided. The light emitting device includes a first semiconductor layer, an uneven part on the first semiconductor layer, a first nonconductive layer including a plurality of clusters on the uneven part, a first substrate layer on the nonconductive layer, and a light emitting structure layer. The light emitting structure layer includes a first conductive type semiconductor layer, an active layer and a second conductive type semiconductor layer on the first substrate layer.