GaN Light-Emitting Device Electrode Adhesion
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Solution Overview
Problem
Gallium nitride-based compound semiconductor light-emitting devices face challenges in maintaining the adhesion of the over-coating layer to the p-type semiconductor layer, leading to exfoliation at corner portions, which affects productivity and light-emission efficiency.
Innovation Solution
The positive electrode design features an over-coating layer that contacts the p-type semiconductor layer more extensively at corner portions than at side portions, reducing the likelihood of exfoliation and allowing for a larger first electrode area, thereby enhancing light-emission output and reducing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stabilizer layer is made to cover most of the p-type semiconductor layer to prevent exfoliation, then the adhesion is improved, but the reflection factor decreases because the stabilizer layer has lower reflectivity than Ag or Al
Solution Approach 1:
The patent applies different contact area ratios of the stabilizer layer to the p-type semiconductor layer at different locations: at corner portions, the contact area ratio is set to 20-80% to prevent exfoliation, while at side portions, the contact area ratio is set to 0-10% to maintain high reflection factor. This local differentiation resolves the contradiction between adhesion and reflectivity.
2Illumination intensity
If the silver layer is made as wide as possible to achieve high reflection factor, then the reflection factor is improved, but the area where the stabilizer layer contacts the p-type semiconductor layer becomes too small, causing exfoliation
Solution Approach 1:
The patent differentiates the stabilizer layer contact area ratio between corner portions (20-80%) and side portions (0-10%), allowing the silver layer to be wide for high reflectivity while ensuring sufficient stabilizer contact at corners to prevent exfoliation.
3Strength
If dents are formed in the p-type semiconductor layer to prevent exfoliation, then the adhesion is improved, but the productivity decreases due to additional processing steps
Solution Approach 1:
The patent extracts the adhesion-enhancing function from the semiconductor layer structure (dents) and transfers it to the electrode structure (stabilizer layer contact area ratio), eliminating the need for additional dent-forming processing steps while maintaining adhesion prevention capability.
Solution Approach 2:
The patent changes the geometric parameter of the stabilizer layer (contact area ratio) from a uniform structure to a differentiated structure with specific ratios at corner and side portions, achieving adhesion prevention without modifying the semiconductor layer structure or adding processing steps.
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 design results in fewer defective devices during production, improved yield, increased light-emission output, and lower driving voltage, making the gallium nitride-based compound semiconductor light-emitting device more efficient and productive.
Implementation Method 1
the positive electrode 10 is made of a reflecting metal and is provided to cover most of the p-type semiconductor layer 5, so that light heading toward the positive electrode side from the light-emitting layer is reflected by the positive electrode 10 and leaves from the side of the substrate 1
Implementation Method 2
the stabilizer layer must be adhered to the p-type semiconductor layer while maintaining a large adhering strength
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An object of the present invention is to provide a gallium nitride-based compound semiconductor light-emitting device having a positive electrode which comprises a first electrode and an over-coating layer covering the side surfaces and upper surface of the first electrode provided on a p-type semiconductor layer, the over-coating layer tending not to be exfoliated from the p-type semiconductor layer. The inventive gallium nitride-based compound semiconductor light-emitting device comprises an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer of gallium nitride-based compound semiconductors which are formed in this order on a substrate, the negative electrode and the positive electrode being provided in contact with the n-type semiconductor layer and the p-type semiconductor layer, respectively, wherein the positive electrode comprises at least a first electrode and an over-coating layer covering the side surfaces and upper surface of the first electrode, and the area where the over-coating layer comes into contact with the p-type semiconductor layer is greater at the corner portions of the positive electrode than at the side portions thereof, per unit length of the outer edge of the first electrode.