Semiconductor Light Emitting Element Silver Migration Barrier
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Solution Overview
Problem
The use of silver in reflection layers in semiconductor light emitting elements can lead to migration, causing roughness at the interface and reducing reflectance, which in turn decreases light extraction efficiency in flip-chip bonded devices.
Innovation Solution
A semiconductor light emitting element is designed with a transparent conductive layer of indium oxide or zinc oxide, a silver or silver alloy metal layer for reflection, and a conductive oxide layer for electrical connection, where the layers are structured to avoid direct contact and exposure, maintaining optical permeability and conductivity while preventing silver migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is formed on the reflection layer containing silver to protect it, then the silver layer is protected from degradation, but the reflectance is reduced due to generation of roughness on the interface caused by silver migration
Solution Approach 1:
A barrier layer composed of a metal oxide having optical permeability and conductivity is introduced between the transparent conductive layer and the silver-containing reflection layer. This intermediary layer prevents silver migration to the interface while maintaining optical transparency and electrical conductivity, thus protecting the reflectance and light extraction efficiency without compromising the protection function.
2Illumination intensity
If silver is used in the reflection layer, then high reflectance is achieved, but silver migration causes interface roughness and reduces reflectance over time
Solution Approach 1:
The barrier layer acts as a mediator that stabilizes the interface between the transparent conductive layer and the silver reflection layer. It prevents silver atoms from migrating across the interface while maintaining the high reflectance properties of the silver layer, thus achieving both high illumination intensity and long-term compositional stability.
Solution Approach 2:
The use of a metal oxide barrier layer with specific properties (optical permeability and conductivity) creates a composite structure that combines the protective function with the optical and electrical requirements. This composite approach allows the system to maintain high reflectance while preventing degradation through material composition design.
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 configuration effectively suppresses the reduction in light extraction efficiency by maintaining the reflectance and optical properties of the silver layer, ensuring efficient light output in flip-chip bonded semiconductor light emitting elements.
Implementation Method 1
a light emitting layer that emits light by conduction
Implementation Method 2
a transparent conductive layer that is composed of a metal oxide having optical permeability to the light emitted from the light emitting layer and conductivity
Implementation Method 3
a metal layer that is composed of any one of silver and an alloy containing silver and is laminated on the transparent conductive layer
Data Source
AI summary
A semiconductor light emitting element (1) including of a substrate (110) composed of sapphire; a laminated semiconductor layer (100) composed of an n-type semiconductor layer (140), a light emitting layer (150) and a p-type semiconductor layer (160) provided on the substrate (110); a first electrode (170) formed in the p-type semiconductor layer (160); and a second electrode (180) formed in the n-type semiconductor layer (140). Further, the first electrode (170) includes a first conductive layer (171) composed of an oxide transparent conductive material laminated on the p-type semiconductor layer (160); a reflection layer (172) which contains silver laminated on the first conductive layer (171); a second conductive layer (173) composed of an oxide conductive material laminated on the reflection layer (172); and a coating layer (174) provided so as to cover the first conductive layer (171), the reflection layer (172) and the second conductive layer (173).