Recessed LED N-Electrode for Light Extraction
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Solution Overview
Problem
In light emitting diode (LED) dies, especially vertical LEDs, the n-electrode often blocks and absorbs electromagnetic radiation due to its larger surface area, which reduces electroluminescence intensity, and the fabrication process can lead to decreased effectiveness of light extraction structures and increased electrical resistivity.
Innovation Solution
A recessed n-electrode is embedded in the n-type confinement layer with a smooth planar surface, minimizing surface area and contact resistance, and is fabricated using a method that forms the electrode in a recess to avoid direct deposition on light extraction structures, ensuring high conductivity and low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the n-electrode surface area is increased to ensure adequate electrical connection, then electrical conductivity is improved, but electromagnetic radiation absorption increases and electroluminescence intensity decreases
Solution Approach 1:
The electrode transitions from a planar surface to a three-dimensional structure with vertical sidewalls. By etching recesses into the n-type confinement layer and filling them with conductive material, the electrode gains vertical dimensionality. This allows the electrode to achieve adequate electrical connection through the vertical sidewall surface area while maintaining a small horizontal footprint, thus reducing electromagnetic radiation absorption in the horizontal plane.
2Illumination intensity
If light extraction structures are added to enhance light extraction, then light extraction efficiency is improved, but the electrode surface area increases due to deposition on rough structures
Solution Approach 1:
The recesses are etched into the n-type confinement layer before forming the light extraction structures. By pre-defining the electrode geometry in recesses, the subsequent light extraction structure formation occurs on the exposed sidewalls of these recesses rather than on a planar surface. This preliminary action ensures that when conductive material is deposited, it forms electrodes with reduced horizontal surface area while still providing adequate vertical contact area for electrical connection.
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 design minimizes electromagnetic radiation absorption, enhances light extraction, and reduces contact resistance, resulting in improved electroluminescence intensity and electrical conductivity while maintaining a planar morphology.
Implementation Method 1
a multiple quantum well (MQW) layer located between the confinement layers configured to emit electromagnetic radiation
Implementation Method 2
the n-type confinement layer 12 includes light extraction structures 24 in the form of multi faceted elements that provide light scattering
Data Source
AI summary
A light emitting diode (LED) die includes a semiconductor substrate having an n-type confinement layer, a multiple quantum well (MQW) layer in electrical contact with the n-type confinement layer configured to emit electromagnetic radiation, a p-type confinement layer in electrical contact with the multiple quantum well (MQW) layer; multiple light extraction structures on the n-type confinement layer configured to scatter the electromagnetic radiation; and an electrode in a recess embedded in the n-type confinement layer proximate to the light extraction structures. A method of fabrication includes: forming the semiconductor substrate; forming a recess in the n-type confinement layer having sidewalls and a planar bottom surface; forming an electrode in the recess comprising a conductive material conforming to the sidewalls and to the bottom surface of the recess; planarizing the electrode; and forming a plurality of light extraction structures in the n-type confinement layer proximate to the electrode.