Inverted Large Scale Light Extraction Structures
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Solution Overview
Problem
Semiconductor emitting devices, such as LEDs and laser diodes, face issues with light trapping due to abrupt changes in optical properties and refractive indices between layers, leading to significant light absorption and reduced efficiency.
Innovation Solution
The introduction of an interface with profiled surfaces featuring large and small roughness components, where the first characteristic scale is approximately an order of magnitude larger than the second, facilitates light extraction by providing additional surfaces for reflection and refraction, reducing total internal reflection and Fresnel losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If smooth interfaces are used between layers, then manufacturing is easier, but light extraction is reduced due to total internal reflection and Fresnel losses
Solution Approach 1:
The patent applies surface curvature by introducing roughness components with specific radius of curvature values. The first roughness component has a radius of curvature between 1-10 micrometers and the second has 0.1-1 micrometer, creating curved surfaces that reduce total internal reflection and improve light extraction efficiency while maintaining manufacturability through controlled fabrication processes.
2Device complexity
If single-scale roughness is used, then fabrication is simpler, but light extraction across different angles and wavelengths is insufficient
Solution Approach 1:
The patent segments the interface roughness into two distinct scales: first roughness components with 1-10 micrometer radius of curvature and second roughness components with 0.1-1 micrometer radius of curvature. This segmentation allows different roughness scales to address different light extraction mechanisms, with larger roughness handling broader angle extraction and smaller roughness addressing specific wavelength optimization, thereby improving overall light extraction efficiency.
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 configuration enhances the propagation and extraction of radiation, increasing the amount of light that escapes the device, thereby improving the overall efficiency of light emitting diodes and laser diodes.
Implementation Method 1
A larger change in the index of refraction between the layers, and between the substrate and its surroundings, results in a smaller total internal reflection (TIR) angle
Implementation Method 2
Fresnel losses are associated with light partially reflected at the interface for all the incident light angles
Implementation Method 3
providing additional surfaces through which light can escape without totally internally reflecting from the interface
Data Source
AI summary
An interface including roughness components for improving the propagation of radiation through the interface is provided. The interface includes a first profiled surface of a first layer comprising a set of large roughness components providing a first variation of the first profiled surface having a first characteristic scale and a second profiled surface of a second layer comprising a set of small roughness components providing a second variation of the second profiled surface having a second characteristic scale. The first characteristic scale is approximately an order of magnitude larger than the second characteristic scale. The surfaces can be bonded together using a bonding material, and a filler material also can be present in the interface.