Nitride Semiconductor Light Extraction Surface with Oblique Angles
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Solution Overview
Problem
Existing semiconductor light emitting devices face challenges in heat dissipation performance and light extraction efficiency, particularly when using nitride-based group III-V compound semiconductors on sapphire or SiC substrates, where strong alkali etching for rough surfaces erodes not only the light emitting surface but also electrodes and other components.
Innovation Solution
A semiconductor light emitting device with a nitride-based III-V compound semiconductor on a substrate, featuring a light extraction surface processed into an uneven shape with multiple oblique angles to enhance light extraction efficiency while minimizing stress during substrate peeling, using a laser lift-off method and specific electrode and refractive-index relaxation film configurations to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If strong alkali etching is used to process the light emitting surface to make it rough, then light extraction efficiency is improved, but electrodes and other components are eroded
Solution Approach 1:
The patent applies preliminary action by forming the rough light extraction surface on the substrate before bonding the compound semiconductor layer. This is achieved through dry etching or mechanical polishing of the substrate surface, creating protrusions and recesses that will later enhance light extraction. By preparing the rough surface in advance rather than after bonding, the patent avoids exposing electrodes and other components to corrosive etchants, thus preventing erosion while still achieving the desired light extraction enhancement.
2Temperature
If the substrate is peeled off by laser lift-off method, then heat dissipation performance is improved, but stress concentration may damage the compound semiconductor layer
Solution Approach 1:
The patent applies beforehand cushioning by forming a stress relief layer between the substrate and the compound semiconductor layer. This stress relief layer absorbs and distributes the stress generated during laser lift-off substrate peeling, preventing stress concentration that would otherwise damage the compound semiconductor layer. The stress relief layer acts as a buffer that cushions the mechanical stresses, allowing the substrate to be removed for improved heat dissipation while protecting the integrity of the semiconductor structure.
3Ease of manufacture
If a flat light emitting surface is used, then manufacturing process is simple, but light extraction efficiency is low
Solution Approach 1:
The patent applies spheroidality by forming a rough surface with protrusions and recesses on the light extraction surface instead of using a flat surface. The curved surfaces of the protrusions scatter light in multiple directions, increasing the probability of light extraction from the high-refractive-index compound semiconductor layer. This curvature-based approach significantly enhances light extraction efficiency compared to flat surfaces, while the protrusions can be formed through established techniques like dry etching or mechanical polishing.
4Manufacturing precision
If electrodes and components are protected from etching, then manufacturing precision is maintained, but additional process steps are required
Solution Approach 1:
The patent applies preliminary action by forming the rough light extraction surface on the substrate before bonding the compound semiconductor layer and its associated electrodes and components. By preparing the rough surface in advance through dry etching or mechanical polishing of the substrate, the patent eliminates the need for subsequent protective masking and etching steps that would be required if the rough surface were created after bonding. This sequential reordering of operations maintains manufacturing precision while actually simplifying the overall process integration.
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 significantly improves light extraction efficiency by two times or more compared to flat surfaces, while reducing stress and preventing damage to the compound semiconductor layer during substrate peeling, thus enhancing the device's performance and integration process.
Implementation Method 1
peeling off the substrate by a laser lift-off method
Data Source
AI summary
A semiconductor light emitting device has a light emitting element, and first and second electrodes. The light emitting element has a nitride-based III-V compound semiconductor on a substrate. The first and second electrodes are disposed on both sides of the light emitting element, respectively. The light emitting element has a light emitting layer, a first conductive type semiconductor layer, and a second conductive type semiconductor layer. The first conductive type semiconductor layer is disposed between the light emitting layer and the first electrode. The second conductive type semiconductor layer is disposed between the light emitting layer and the second electrode. One surface of the first conductive type semiconductor layer contacts the first electrode and is a light extraction surface which is roughly processed so as to have two or more kinds of oblique angles.