LED Substrate Inclined Sidewalls Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light emitting diodes (LEDs) suffer from low light extraction efficiency due to total internal reflection of photons within the semiconductor structure, leading to absorption and reduced output.
Innovation Solution
The method involves epitaxially growing a light emitting structure on a substrate and scribing it to form angled side surfaces, where the surface tangent vector forms angles between approximately ten and eighty degrees with the substrate normal, followed by cleaning to enhance light extraction by mitigating total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LED emits light uniformly in different directions, then light is emitted in all directions, but most light is totally internally reflected and trapped in the semiconductor structure
Solution Approach 1:
The patent applies asymmetry by forming inclined sidewalls on the LED substrate at specific angles (10-80 degrees from vertical) to break the symmetry of light propagation. This asymmetric geometry redirects light paths to escape the total internal reflection that occurs in conventional planar LEDs, thereby improving light extraction efficiency while reducing light trapping losses.
Solution Approach 2:
The patent introduces a dimensional change by transitioning from a planar (2D) substrate surface to a three-dimensional structure with inclined sidewalls. This geometric modification adds angular dimensionality to light extraction, creating additional escape paths for photons that would otherwise be trapped, thus improving light extraction efficiency.
2Illumination intensity
If substrate is scribed to form angled side surfaces, then light extraction efficiency increases, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the inclined sidewalls on the substrate before epitaxial growth of the light-emitting layers. This pre-shaping of the substrate simplifies subsequent fabrication steps, as the light-extraction-optimizing geometry is already in place, reducing overall manufacturing complexity despite the initial shaping step.
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 approach significantly increases light extraction efficiency, with experimental results showing improvements in power and external quantum efficiency, particularly when combined with reflective coatings and optimized scribing angles.
Implementation Method 1
A large fraction of emitted light is totally internally reflected and trapped in the semiconductor structure
Implementation Method 2
semiconductor layers with high indexes of refraction
Implementation Method 3
epitaxially growing a light emitting structure on a surface of a substrate
Data Source
AI summary
A light emitting device having improved light extraction is provided. The light emitting device can be formed by epitaxially growing a light emitting structure on a surface of a substrate. The substrate can be scribed to form a set of angled side surfaces on the substrate. For each angled side surface in the set of angled side surfaces, a surface tangent vector to at least a portion of each angled side surface in the set of angled side surfaces forms an angle between approximately ten and approximately eighty degrees with a negative of a normal vector of the surface of the substrate. The substrate can be cleaned to clean debris from the angled side surfaces.