Semiconductor Light Extraction via Profiled Vacancy Scattering
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Solution Overview
Problem
Semiconductor emitting devices, such as LEDs and laser diodes, face challenges with light extraction due to total internal reflection, leading to light trapping and absorption, which is not effectively alleviated by conventional roughness elements that affect both trapped and escape rays.
Innovation Solution
A semiconductor structure with a transparent layer having a profiled surface featuring vacancies with side walls configured for partial diffusive scattering of radiation, allowing improved light propagation and extraction by optimizing the size and distance of roughness elements to minimize absorption and enhance escape efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional roughness elements are used at the interface, then light extraction is partially improved, but both trapped rays and escape rays are affected, leading to reduced output power
Solution Approach 1:
The patent applies local quality by creating vacancies with specific geometric characteristics (depth, diameter, spacing) at particular locations within the semiconductor layer. These vacancies are strategically positioned to preferentially interact with trapped rays through diffusive scattering, while minimizing interference with escape rays that are already on extraction paths. The local modification of the interface structure allows differentiated treatment of different ray populations.
Solution Approach 2:
The vacancies act as intermediary structures that mediate between the trapped rays and the escape rays. By introducing these vacuum cavities with specific geometric parameters, the patent creates intermediate scattering centers that selectively redirect trapped rays without significantly affecting escape rays, thus serving as a mediator that resolves the conflict between light extraction improvement and output power maintenance.
2Loss of energy
If the size of roughness elements is increased to improve light scattering, then trapped rays are more effectively scattered, but absorption by layers and metal contacts increases
Solution Approach 1:
The patent employs parameter changes by precisely controlling the geometric parameters of the vacancies (depth, diameter, spacing, shape) to optimize their scattering effectiveness. By adjusting these parameters, the vacancies achieve efficient diffusive scattering of trapped rays while maintaining appropriate size relationships that prevent excessive absorption. The parameter optimization ensures that vacancies are large enough to scatter trapped rays effectively but small and appropriately spaced to avoid creating additional absorption pathways.
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 diffusively scattering trapped rays while minimizing the impact on escape rays, resulting in enhanced output power and reduced absorption within the device.
Implementation Method 1
Each vacancy comprises side walls configured for at least partial diffusive scattering of the radiation of the target wavelength
Implementation Method 2
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 3
Roughness at an interface allows for partial alleviation of the light trapping by providing additional surfaces through which light can escape without totally internally reflecting from the interface
Implementation Method 4
Fresnel losses are associated with light partially reflected at the interface for all the incident light angles. Optical properties of the materials on each side of the interface determines the magnitude of Fresnel losses
Data Source
AI summary
A semiconductor structure for use in fabricating a semiconductor device having improved light propagation is provided. The structure includes at least one layer transparent to radiation having a target wavelength relevant to operation of the semiconductor device. During operation of the semiconductor device, radiation of the target wavelength enters the transparent layer through a first side and exits the transparent layer through a second side. At least one of the first side or the second side comprises a profiled surface. The profiled surface includes a plurality of vacancies fabricated in the material of the layer. Each vacancy comprises side walls configured for at least partial diffusive scattering of the radiation of the target wavelength.