LED Chip Reflective Layer Gradients for Adhesion and Reflectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED technology faces challenges in maximizing light extraction efficiency due to internal absorption of photons and limited current spreading within the LED chip structures, leading to issues such as electromigration, low adhesion, and delamination of metal reflective layers.
Innovation Solution
A metal reflective layer is formed with a first metal promoting increased reflectivity and a second metal enhancing mechanical stability and adhesion, featuring a nonuniform distribution throughout the layer with concentration gradients near interfaces, achieved through sequential deposition and annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform metal reflective layer is used, then the manufacturing process is simple, but the adhesion and mechanical stability are insufficient
Solution Approach 1:
The patent applies local quality by creating a nonuniform distribution of the second metal within the metal reflective layer. The second metal concentration varies through the thickness of the layer, with higher concentrations near interfaces to adhesion layers or dielectric reflective layers. This localized concentration strategy enhances adhesion and mechanical stability at critical interfaces while maintaining manufacturing feasibility through sequential deposition processes.
2Device complexity
If a single metal is used in the reflective layer, then the structure is simple, but the electromigration resistance is insufficient
Solution Approach 1:
The patent employs composite materials by combining a first metal and a second metal within the metal reflective layer. The first metal provides high reflectivity while the second metal, distributed nonuniformly throughout the layer, provides enhanced electromigration resistance. This composite structure achieves improved reliability without excessive complexity, as the sequential deposition process is compatible with existing manufacturing capabilities.
3Productivity
If light emission efficiency is maximized, then more light is extracted in the desired direction, but internal absorption of photons increases
Solution Approach 1:
The patent applies local quality by concentrating the second metal near the interfaces of the metal reflective layer, particularly where it contacts adhesion layers or dielectric reflective layers. This localized distribution optimizes the functional properties at critical interfaces for light extraction while minimizing bulk material that could cause internal absorption. The nonuniform concentration profile ensures high reflectivity and adhesion where needed without sacrificing light extraction efficiency.
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 solution enhances light reflectivity, mechanical stability, and reduces electromigration, thereby improving the operational performance and longevity of LED chips.
Implementation Method 1
sequential deposition and annealing processes
Implementation Method 2
annealing to form the metal reflective layer
Implementation Method 3
The first metal may promote increased reflectivity relative to the second metal
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and more particularly reflective structures for LED chips and related methods are disclosed. Reflective structures include arrangements of a first metal and a second metal within a metal reflective layer. The second metal may have a nonuniform distribution throughout a thickness of the metal reflective layer relative to the first metal. The first metal may promote increased reflectivity relative to the second metal, and the second metal may promote increased mechanical stability, increased adhesion, and reduced electromigration. An exemplary metal reflective layer includes increased concentrations of the second metal near interfaces between the metal reflective layer and other layers of the LED chip. The second metal may also form concentration gradients in directions away from the interfaces. Related methods include sequentially forming discrete layers of the first and second metals, followed by annealing to form the metal reflective layer.