GaN LED Cap Structure Reflective Layer Light Extraction
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Solution Overview
Problem
Gallium nitride (GaN) light emitting diodes (LEDs) require improved light extraction efficiency to be effective in general lighting applications.
Innovation Solution
A light emitting device structure featuring a substrate, buffer layer, semiconductor mesa with a light emitting active layer, contact layer, passivation layer, and a cap structure with a reflective layer and solder layer, designed to enhance light extraction by reflecting light generated by the active layer towards the buffer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED structure is used, then the device is simple to manufacture, but the light extraction efficiency is insufficient for general lighting applications
Solution Approach 1:
The LED structure is divided into distinct functional segments: a mesa structure for light generation, a cap structure with reflective layer for light redirection, and a solder layer with recess for enhanced light extraction. This segmentation allows each component to be optimized for its specific function while maintaining manufacturability through standardized fabrication processes.
Solution Approach 2:
The patent introduces a vertical cap structure with a reflective layer that redirects light in the vertical dimension, and a solder layer with a recess that creates additional light extraction pathways. This dimensional approach transforms light propagation from primarily lateral to including vertical components, significantly improving light extraction efficiency without complicating the horizontal manufacturing process.
2Productivity
If light extraction efficiency is improved through additional structures, then lighting performance is enhanced, but device complexity increases
Solution Approach 1:
The cap structure merges multiple functions into a single integrated component: the reflective layer for light redirection, the solder layer for electrical connection and additional light extraction, and the recess feature for enhanced light coupling. This merging reduces the number of separate components and fabrication steps compared to implementing each function separately, thereby limiting the increase in device complexity.
Solution Approach 2:
The solder layer serves multiple purposes: providing electrical connection, acting as an additional light extraction interface through its recess structure, and serving as a bonding interface for packaging. This multi-functionality reduces the need for separate components, thereby improving light extraction efficiency without proportionally increasing device complexity.
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 described structure improves light extraction efficiency of GaN LEDs, enhancing their performance for general lighting applications by effectively reflecting light towards the buffer layer.
Implementation Method 1
a cap structure with a reflective layer and a solder layer with a recess in which the reflective layer is disposed, where the recess is configured to improve light extraction by reflecting light generated by the active layer towards the buffer layer
Data Source
AI summary
A light emitting device and method of forming the same, the light emitting device including: a substrate, a buffer layer disposed on the substrate, a semiconductor mesa disposed on the buffer layer and including a first semiconductor layer, a light emitting active layer disposed on the first semiconductor layer, and a second semiconductor layer disposed on the first semiconductor layer, a contact layer disposed on an upper surface of the mesa, a passivation layer covering sidewalls of the mesa and the contact layer, and a cap structure including a reflective layer covering an upper surface of the contact layer, and a solder layer including a recess in which the reflective layer is disposed.