Semiconductor Light-Emitting Element Ag Migration Barrier
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Solution Overview
Problem
Semiconductor light-emitting elements with reflective metal layers, such as those containing Ag, suffer from Ag migration issues that degrade the reliability and light extraction efficiency due to the metal's propensity to migrate and react with other layers.
Innovation Solution
A semiconductor light-emitting element structure featuring an ohmic electrode layer, a reflective metal layer containing Ag that covers at least the ends of the ohmic electrode layer, and a covering electrode layer made of conductive oxide films to reliably bury and protect the reflective metal layer, preventing Ag migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective metal layer containing Ag is formed on the p-type semiconductor layer to improve light extraction efficiency, then light extraction efficiency is improved, but Ag migration occurs which degrades reliability
Solution Approach 1:
An Al layer is introduced as an intermediary barrier layer between the Ag reflective metal layer and the p-type semiconductor layer. This Al layer prevents Ag atoms from migrating into the semiconductor layer while maintaining the light-reflecting function of the Ag layer, thus resolving the contradiction between light extraction efficiency and reliability
Solution Approach 2:
The electrode structure is designed as a composite multi-layer system comprising Ag layer, Al layer, and p-type semiconductor layer. The combination of different materials (Ag for reflectivity, Al for barrier properties) creates a structure that simultaneously achieves high light extraction efficiency and prevents Ag migration, resolving the reliability issue
2Illumination intensity
If Ag is used as reflective metal to achieve high light reflectivity, then light extraction efficiency is improved, but Ag easily migrates to other layers causing degradation in electric properties
Solution Approach 1:
The Al layer serves as a mediator that blocks the migration path of Ag atoms while allowing the Ag layer to maintain its light-reflecting function. This intermediary barrier prevents the harmful Ag migration effect without compromising the beneficial light reflectivity
Solution Approach 2:
The Al barrier layer is placed in advance between the Ag layer and semiconductor layer to preemptively prevent Ag migration before it can occur. This preliminary protective action stops the harmful migration process at its source, maintaining both reflectivity and electrical properties
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 enhances the reliability and light extraction efficiency by preventing Ag migration and ensuring stable electrical properties while maintaining high light reflection and emission uniformity.
Implementation Method 1
a reflective metal layer containing Ag is formed so as to cover at least ends of the ohmic electrode layer
Data Source
AI summary
A semiconductor light-emitting element includes: an ohmic electrode layer formed on a surface of a semiconductor structure layer including a light-emitting layer; a reflective metal layer containing Ag formed so as to cover at least ends of the ohmic electrode layer; and a covering electrode layer formed so as to bury the reflective metal layer.