Nano Rod LED Light Extraction via Segmented Nanorods
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in light extraction efficiency due to total internal reflection, which limits their output and degrades their characteristics, and existing methods to improve this efficiency, such as surface texturing, are complex and require precise control, while also being sensitive to temperature and current variations.
Innovation Solution
The development of a nano rod type LED with active layers formed into spaced apart rods, where a second polarity layer wraps around each rod, increasing the light emitting area and reducing total internal reflection, along with the use of a current transport enhanced layer and transparent conductive oxide film to enhance carrier mobility and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional planar LED structure is used, then the device is simple to fabricate, but light extraction efficiency is poor due to total internal reflection
Solution Approach 1:
The active layer is divided into multiple independently grown nanorod structures instead of a continuous planar layer. Each nanorod acts as an independent light-emitting unit with its own p-n junction, enabling light to be emitted from the sidewalls and tops of the nanorods, thereby reducing total internal reflection and improving light extraction efficiency while maintaining fabrication simplicity through vapor-phase growth processes
Solution Approach 2:
The invention transitions from a two-dimensional planar active layer to a three-dimensional array of nanorods. This dimensional change creates additional light extraction pathways by emitting light from the sidewalls and tops of the nanorods in multiple directions, effectively reducing the impact of total internal reflection that plagues conventional planar structures
2Loss of energy
If surface texturing techniques are used to improve light extraction, then light extraction efficiency increases, but device complexity and manufacturing precision requirements increase
Solution Approach 1:
The nanorod structures are grown self-organizingly through vapor-phase epitaxial processes, where the nanorods spontaneously form with controlled spacing and uniform dimensions without requiring external patterning masks or complex texturing steps. This self-organized growth inherently creates the desired light-extraction-enhancing structure while avoiding the complexity of conventional surface texturing fabrication processes
Solution Approach 2:
The invention replaces mechanical patterning methods (such as photolithography and etching used in surface texturing) with a chemical vapor-phase growth process. The nanorods are formed through controlled chemical reactions in the vapor phase, eliminating the need for complex mechanical patterning steps and reducing manufacturing precision requirements while achieving superior light extraction efficiency
3Loss of energy
If the light emitting area is increased to improve light output, then more light can be extracted, but the device structure becomes more complex
Solution Approach 1:
The invention merges the functions of multiple components into the nanorod structure itself: the nanorod body serves as the active layer, the sidewalls provide additional light emission surfaces, and the overall array configuration maximizes light extraction. This integration achieves a large effective light-emitting area without requiring separate components or complex multi-layer structures, thereby improving light output while maintaining structural simplicity
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 approach significantly improves light extraction efficiency by increasing the light emitting area, reducing total internal reflection, and enhancing thermal and crystalinity characteristics, resulting in superior light output and emission efficiency.
Implementation Method 1
Light generated in a light emitting diode is mostly confined inside the diode due to total internal reflection with a critical angle at an interface between two media such as a semiconductor and air
Implementation Method 2
an active layer (320) and a compound semiconductor layer (330) doped with a second polarity dopant are sequentially formed on each of the rods (310) to form a light emitting structure (350)
Data Source
Figure 1~2
Figure 3a~3c
Figure 4~6
AI summary
A rod type light emitting device and a method for fabricating the same are disclosed, wherein the rod type light emitting diode comprises a metallic support layer, a first electrode on the metallic support layer, a plurality of rod structures on the first electrode and a second electrode on the plurality of rod structures, wherein the rod structure comprises a first polarity semiconductor layer, an active layer and a second polarity semiconductor layer whose polarity is opposite to that of the first polarity semiconductor layer and being separated one another.