Semiconductor Light Emitting Element Asymmetric Electrode Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The light extraction efficiency of semiconductor light emitting elements, such as LEDs, is limited due to light absorption by the substrate and the front surface electrode, which also affects current spreading and forward voltage, especially in smaller chip sizes where the electrode shape can hinder light output.
Innovation Solution
A semiconductor light emitting element design featuring a group III-V compound semiconductor layer with a reflection metal film sandwiched between the light emitting layer and a support substrate, incorporating a compact front surface electrode and an ohmic contact joint part positioned to minimize light absorption, along with a transparent dielectric reflection part to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the area of the front surface electrode is reduced to minimize light absorption, then light extraction efficiency is improved, but current spreading property deteriorates
Solution Approach 1:
The front surface electrode is designed with an asymmetric shape (e.g., semicircular or D-shaped) rather than a simple circular shape, allowing one end to extend closer to the light emitting layer while the other end remains farther away. This asymmetric configuration reduces the overall electrode area to minimize light absorption while maintaining sufficient current spreading path through the asymmetric geometry that provides both compactness and extended current distribution zones.
2Ease of manufacture
If a simple circular shape is used for the front surface electrode, then manufacturing is easier, but current spreading property deteriorates when area is reduced
Solution Approach 1:
The electrode transitions from a simple circular shape to an asymmetric shape (semicircular or D-shaped) that maintains manufacturing feasibility while improving current spreading. The asymmetric design allows the electrode to have both a compact region (for reduced light absorption) and an extended region (for improved current spreading), achieving a balance between ease of manufacture and electrical performance.
3Loss of energy
If high reflectivity metal is used for the reflection metal film, then light extraction efficiency is improved, but ohmic contact capability is lost
Solution Approach 1:
The bottom electrode structure is segmented into functionally distinct regions: a reflection metal film region (with high reflectivity materials like Al, Au, or Ag) and an ohmic contact joint part region (with good ohmic contact materials). This segmentation allows each region to perform its specialized function optimally - the reflection metal film minimizes light absorption while the ohmic contact joint part ensures reliable electrical contact with the compound semiconductor layer.
Solution Approach 2:
Different material properties are assigned to different locations of the bottom electrode. The reflection metal film is positioned where high reflectivity is needed (under the light emitting layer), while the ohmic contact joint part is positioned where good electrical contact is needed (at the contact interface with the semiconductor). This local quality differentiation resolves the contradiction between light reflection and ohmic contact capabilities.
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 design significantly improves light extraction efficiency and reduces forward voltage by optimizing the electrode shape and placement, while maintaining effective current spreading, particularly in smaller chip sizes.
Implementation Method 1
a reflection metal film formed on the second main surface for reflecting a light emitted from the light emitting layer toward the light extraction surface
Implementation Method 2
electron or hole injected into the LED element moves through a front surface electrode formed on the light emitting part and the ohmic contact joint part to the Si support substrate
Implementation Method 3
a transparent dielectric reflection part formed between the group III-V compound semiconductor layer and the front surface electrode
Data Source
AI summary
A semiconductor light emitting element includes a group III-V compound semiconductor layer, a first main surface and a second main surface, a reflection metal film formed on the second main surface, a front surface electrode formed on the first main surface, and an ohmic contact joint part formed between the reflection metal film and the group III-V compound semiconductor layer except a region directly under the front surface electrode. The ohmic contact joint part is disposed in a side of an outer peripheral part of the semiconductor light emitting element, formed so as to surround the front surface electrode when the ohmic contact joint part is viewed from a side of the front surface electrode, and disposed so that distance from each location of outer edge parts of the front surface electrode to the ohmic contact joint part nearest to the each location becomes equal to each other.