GaN LED Current Spreading Layer Design
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Solution Overview
Problem
Current GaN-based vertical LEDs face limitations in luminous efficiency due to current crowding, which restricts the effective improvement of light-emitting performance and static breakdown voltage.
Innovation Solution
The LED structure incorporates a compound multi-current spreading layer with alternatively-laminated u-type and n-type nitride semiconductor layers, including a distributed insulation layer, to uniformly spread current over the light-emitting area, addressing current crowding and enhancing current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional single-layer current spreading layer is used, then the structure is simple, but current crowding occurs and light-emitting efficiency is limited
Solution Approach 1:
The current spreading layer is divided into multiple sub-layers with different doping concentrations and material compositions. Each sub-layer has a specific function: the first sub-layer (higher doping concentration) handles current injection and initial spreading, while the second sub-layer (lower doping concentration) provides further current distribution and reduces crowding. This segmentation allows the system to achieve both structural manageability and improved current distribution, resolving the contradiction between simplicity and efficiency.
Solution Approach 2:
Different regions of the current spreading layer are designed with locally optimized properties. The first sub-layer has higher doping concentration near the contact region to facilitate current injection, while the second sub-layer has lower doping concentration in the light-emitting region to reduce current crowding. This local quality variation enables the structure to simultaneously maintain electrical conductivity where needed and reduce current density where light emission occurs, improving overall light-emitting efficiency without excessive complexity.
2Productivity
If a compound multi-current spreading layer is used, then light-emitting efficiency and static breakdown voltage improve, but device complexity increases
Solution Approach 1:
The patent systematically varies key parameters across the current spreading layer sub-layers, including doping concentration (higher in first sub-layer, lower in second), material composition (different Al content in AlGaN), and layer thickness. These parameter changes create a gradient structure that optimizes current distribution and reduces current crowding, achieving improved light-emitting efficiency and static breakdown voltage while maintaining a relatively manageable multi-layer structure.
Solution Approach 2:
The current spreading layer is constructed as a composite structure using different AlGaN alloy compositions with varying aluminum content. The first sub-layer uses one composition ratio optimized for electrical conductivity, while the second sub-layer uses a different composition ratio optimized for current spreading and reduced crowding. This composite material approach enables simultaneous optimization of electrical and optical properties, achieving improved performance despite increased structural complexity.
3Device complexity
If current crowding is not addressed, then the device structure remains simple, but static breakdown voltage is limited
Solution Approach 1:
The current spreading layer is segmented into multiple sub-layers with progressively varying doping concentrations and material properties. This segmentation creates a gradual transition zone that distributes current more evenly across the device, preventing current crowding at any single point. The result is improved static breakdown voltage as current is no longer concentrated in high-stress regions, while the segmented structure remains relatively simple to fabricate using standard MOCVD techniques.
Solution Approach 2:
The patent employs parameter changes across the current spreading layer, particularly in doping concentration and Al content, to create an electric field distribution that prevents current crowding. By gradually varying these parameters from the contact region toward the light-emitting region, the structure achieves higher static breakdown voltage without requiring complex multi-component systems, maintaining relative structural simplicity while improving reliability.
Data Source
AI summary
A lighting emitting diode including: an n side layer and a p side layer formed by nitride semiconductors respectively; an active layer comprising a nitride semiconductor is between the n side layer and the p side layer; wherein, the n-side layer is successively laminated by an extrinsically-doped buffer layer and a compound multi-current spreading layer; the compound multi-current spreading layer is successively-laminated by a first current spreading layer, a second current spreading layer and a third current spreading layer; the first current spreading layer and the third current spreading layer are alternatively-laminated layers comprising a u-type nitride semiconductor layer and an n-type nitride semiconductor layer; the second current spreading layer is a distributed insulation layer formed on the n-type nitride semiconductor layer; and the first current spreading layer is adjacent to the extrinsically-doped buffer layer; and the third current spreading layer is adjacent to the active layer.