Semiconductor Growth Layer Protrusions for Light Extraction
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Solution Overview
Problem
Semiconductor structures, particularly in optoelectronic devices like LEDs and laser diodes, face issues with light trapping due to abrupt changes in refractive index between layers, leading to significant Fresnel losses and absorption, which can be alleviated but not fully resolved by existing roughness techniques.
Innovation Solution
A growth layer with protruding domains is introduced, where these domains have internal regions with a lower refractive index than the surrounding material, allowing for improved light extraction and reduced light trapping by manipulating the refractive index profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a discrete change in molar fractions is used at the interface between two semiconductor layers, then the manufacturing process is simplified, but light trapping occurs due to abrupt changes in refractive index
Solution Approach 1:
The patent applies local quality by creating a graded interface region where the molar fractions of semiconductor alloys change continuously rather than abruptly. This graded composition region is localized at the interface between two semiconductor layers, providing different optical properties (gradual refractive index transition) precisely where needed, while the bulk layers maintain their discrete, well-defined compositions for efficient light generation and transport.
Solution Approach 2:
The patent implements parameter changes by continuously varying the molar fractions of alloying elements (such as Al, In, Ga in nitride semiconductors) across the interface region. This continuous parameter change creates a gradient in the refractive index, allowing light to transition smoothly between layers with different optical properties, thereby reducing Fresnel reflections and improving light extraction efficiency.
2Adaptability or versatility
If a larger change in refractive index between semiconductor layers is used, then band gap control is improved, but total internal reflection angle decreases leading to increased light trapping
Solution Approach 1:
The patent applies local quality by creating a graded interface region where the molar fractions of semiconductor alloys change continuously rather than abruptly. This graded composition region is localized at the interface between two semiconductor layers, providing different optical properties (gradual refractive index transition) precisely where needed, while the bulk layers maintain their discrete, well-defined compositions for efficient light generation and transport.
Solution Approach 2:
The patent implements parameter changes by continuously varying the molar fractions of alloying elements (such as Al, In, Ga in nitride semiconductors) across the interface region. This continuous parameter change creates a gradient in the refractive index, allowing light to transition smoothly between layers with different optical properties, thereby reducing Fresnel reflections and improving light extraction efficiency.
3Loss of energy
If interface roughness is introduced to alleviate light trapping, then light extraction is partially improved, but Fresnel losses remain significant and manufacturing complexity increases
Solution Approach 1:
The patent implements parameter changes by continuously varying the molar fractions of alloying elements (such as Al, In, Ga in nitride semiconductors) across the interface region. This continuous parameter change creates a gradient in the refractive index, allowing light to transition smoothly between layers with different optical properties, thereby reducing Fresnel reflections and improving light extraction efficiency.
Solution Approach 2:
The patent applies composite materials by creating an interface region that combines multiple semiconductor alloy compositions with gradually changing molar fractions. This composite graded interface layer integrates the beneficial optical properties of different semiconductor materials, providing a smooth transition zone that reduces light trapping while maintaining structural integrity and compatibility with standard fabrication processes.
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 growth layer with protruding domains enhances light extraction efficiency and reduces absorption, improving the performance of optoelectronic devices by optimizing the refractive index gradient and reducing stress fields in semiconductor layers.
Implementation Method 1
A larger change in the index of refraction between the semiconductor 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. Optical properties of the materials on each side of the interface determine the magnitude of Fresnel losses
Data Source
AI summary
A growth layer having a growth surface with protruding domains is described. The protruding domains can be separated by a substantially flat growth surface located between the protruding domains. A protruding domain can include an internal region that can be filled with a gas and/or can be partially or completely filled with one or more materials that differ from the material of the growth layer, which forms an outer surface of each of the protruding domains.