LED Mesa Sidewall Structures for Light Extraction Redirection
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face limitations in light extraction efficiency due to internal reflection, leading to reduced visible light emission as photons are absorbed rather than exiting the device.
Innovation Solution
The implementation of a repeating pattern of features on the mesa sidewalls of LED chips, combined with reflective structures, redirects laterally propagating light towards a desired emission direction, enhancing light extraction efficiency by reducing absorption and increasing the probability of refraction over internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light is emitted in all directions from the active region, then light generation is maximized, but light extraction efficiency decreases due to internal reflection and absorption at mesa sidewalls
Solution Approach 1:
The mesa sidewall is segmented into multiple discrete features (protrusions or recesses) arranged in a repeating pattern, creating multiple light redirection interfaces that collectively improve light extraction efficiency while maintaining directional control
Solution Approach 2:
The mesa sidewall features are strategically positioned and dimensioned to create specific optical properties at localized regions, where each feature's geometry (width, depth, spacing) is optimized to redirect light from specific incident angles toward the desired emission direction
2Loss of energy
If a repeating pattern of features is formed on mesa sidewalls to redirect light, then light extraction efficiency improves, but device complexity increases
Solution Approach 1:
A repeating pattern of mesa sidewall features is implemented, where identical or similar geometric elements are periodically arranged along the sidewall circumference, simplifying manufacturing while achieving cumulative light redirection effects
Solution Approach 2:
The optical performance is optimized by adjusting parameters of the mesa sidewall features (width, depth, spacing, shape) rather than fundamentally changing the overall device structure, allowing incremental improvement of 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 approach significantly increases the light output of LEDs by redirecting light that would otherwise escape at the mesa sidewalls, resulting in improved emission efficiency and brighter light output.
Implementation Method 1
it has been found useful to pattern, roughen, or otherwise texture certain LED surfaces to provide a varying surface that increases the probability of refraction over internal reflection and thus enhances light extraction out of these surfaces
Implementation Method 2
Certain aspects include reflective structures that are provided on the active LED structures mesas and are further arranged to extend past the active LED structure mesas to cover the repeating pattern of features
Data Source
AI summary
Light-emitting diodes (LEDs), and more particularly edge structures for light shaping in LED chips are disclosed. Edge structures may include a repeating pattern of features that is formed along one or more mesa sidewalls of active LED structure mesas. Such active LED structure mesas may include a p-type layer, an active layer, and at least a portion of an n-type layer. Features of the repeating pattern may be configured with a size and/or shape to promote redirection of laterally propagating light from the active layer at the mesa sidewalls. In this manner, light that may otherwise escape the LED chip at the mesa sidewalls may be redirected toward an intended emission direction for the LED chip. Certain aspects include reflective structures that are provided on the active LED structures mesas and are further arranged to extend past the active LED structure mesas to cover the repeating pattern of features.