LED Light Extraction via Patterned Carbon Nanotube Mask
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) suffer from low extraction efficiency due to the high refractive index of semiconductor materials, causing large-angle light to be internally reflected and trapped, thereby degrading light emission.
Innovation Solution
A method for manufacturing LEDs that involves using a carbon nanotube layer as a mask to grow semiconductor layers, creating a patterned surface with apertures and grooves that enhance light extraction by allowing photons to escape, while reducing dislocation defects and lattice damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional semiconductor materials are used with high refractive index, then the LED structure is simple and easy to manufacture, but light extraction efficiency is low due to internal reflection of large-angle light
Solution Approach 1:
The patent segments the semiconductor layer into multiple regions with different refractive indices by introducing a patterned nanotube layer. This creates alternating high and low refractive index regions that facilitate light extraction while maintaining manufacturing feasibility through a systematic structure.
Solution Approach 2:
The nanotube layer acts as an intermediary substance between the semiconductor materials with different refractive indices. It provides a transition medium that reduces total internal reflection and enables more efficient light extraction without requiring complete restructuring of the semiconductor layers.
2Loss of energy
If a patterned surface with apertures is created to improve light extraction, then light extraction efficiency increases, but dislocation defects and lattice damage occur
Solution Approach 1:
The patent applies local quality by creating apertures and grooves only in specific regions where light extraction is needed, rather than uniformly across the entire surface. The nanotube layer is positioned strategically to provide local refractive index modulation without compromising the overall structural integrity of the semiconductor layers.
Solution Approach 2:
The nanotube layer is deposited on the semiconductor layer before final device assembly, preliminarily establishing the light extraction pathways. This preliminary action allows the structure to be optimized for light extraction while minimizing subsequent processing that could cause damage.
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 approach significantly improves light extraction efficiency by allowing photons to be reflected and extracted from the LED, reducing dislocation defects, and maintaining the structural integrity of the semiconductor layers.
Implementation Method 1
growing a first semiconductor layer, an active layer, and a second semiconductor layer in that order on the epitaxial growth surface
Implementation Method 2
Large-angle light emitted from the active layer may be internally reflected in LEDs, so that a large portion of the light emitted from the active layer will remain in the LEDs
Data Source
AI summary
A light emitting diode includes a first semiconductor layer, an active layer, a second semiconductor layer, an upper electrode, and a lower electrode. The active layer is sandwiched between the first semiconductor layer and the second semiconductor layer. The lower electrode is electrically connected with the first semiconductor layer, and the upper electrode is electrically connected with the second semiconductor layer. A surface of the second semiconductor layer away from the active layer is used as the light extraction surface. A surface of the first semiconductor layer connected with the lower electrode is a patterned surface including a number of grooves.