LED Light Extraction via Metallic Plasma Conversion
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Solution Overview
Problem
Semiconductor structures used in light emitting diodes (LEDs) face low light extraction efficiency due to near field evanescent waves being internally reflected, leading to a significant portion of emitted light remaining within the structure.
Innovation Solution
A semiconductor structure is designed with a substrate, composite semiconductor layer, first and second optical symmetric layers, and a metallic layer, where the optical symmetric layers and metallic layer work together to amplify and extract near field evanescent waves, converting them into metallic plasma that interacts with the active layer to generate additional photons, thereby enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a standard semiconductor structure is used for LED, then the device is simple to manufacture, but light extraction efficiency is low due to internal reflection of near field evanescent waves
Solution Approach 1:
The patent introduces a metallic layer as an intermediary component between the active layer and the external environment. This metallic layer serves as a mediator that converts trapped near field evanescent waves into propagating light through surface plasmon resonance, thereby extracting light that would otherwise be trapped internally. The metallic layer acts as a bridge between the semiconductor structure and the external optical field, resolving the contradiction by adding a specific functional layer to improve light extraction without fundamentally redesigning the entire device.
Solution Approach 2:
The patent modifies the optical parameters of the semiconductor structure by introducing materials with specific refractive indices and metallic properties. By changing the refractive index contrast and introducing surface plasmon resonance conditions through the metallic layer, the optical field distribution and light extraction characteristics are fundamentally altered. This parameter change enables the conversion of evanescent waves to propagating waves, improving light extraction efficiency while maintaining a relatively simple structural addition.
2Productivity
If optical symmetric layers and metallic layer are added to amplify and extract near field evanescent waves, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the optical symmetric layers and metallic layer during the manufacturing process to establish favorable optical conditions before operation. The metallic layer is positioned and configured to resonate with the near field evanescent waves at their generation frequency, and the optical symmetric layers are pre-formed to guide and amplify the extracted light. This preliminary configuration ensures that when light is generated in the active layer, the extraction mechanism is already in place and optimized, thereby increasing photon generation rate without requiring complex real-time control mechanisms.
Solution Approach 2:
The metallic layer serves multiple functions simultaneously: it acts as an electrical contact, a optical extraction layer through surface plasmon resonance, and a reflective element. The optical symmetric layers also perform dual roles of guiding light and providing structural support. By designing components that perform multiple functions, the patent increases photon generation rate through enhanced light extraction while minimizing the increase in device complexity, as the same layers serve multiple purposes rather than requiring separate dedicated components for each function.
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 significantly improves light extraction efficiency by amplifying and converting near field evanescent waves into metallic plasma, leading to increased photon generation and extraction, thus enhancing the overall luminous efficiency of the LED.
Implementation Method 1
near field evanescent waves emitted from the active layer are internally reflected inside the semiconductor structure
Implementation Method 2
amplify and extract near field evanescent waves, converting them into metallic plasma that interacts with the active layer to generate additional photons
Implementation Method 3
near field evanescent waves emitted from the active layer are internally reflected inside the semiconductor structure, so that a large portion of the light emitted from the active layer remain in the semiconductor structure
Data Source
AI summary
A method for making light emitting diode includes following steps. A substrate having an epitaxial growth surface is provided. A first semiconductor layer, an active layer, and a second semiconductor layer is epitaxially grown on the epitaxial growth surface of the substrate in that sequence. A first optical symmetric layer is formed on the second semiconductor layer. A metallic layer is applied on the first optical symmetric layer. A second optical symmetric layer is formed on the metallic layer. The substrate is removed. A first electrode is configured to cover entire exposed surface of the first semiconductor layer. A second electrode is electrically connected to the second semiconductor layer.