Angled Sidewall Growth Substrate for Top-Emitting LED Light Extraction
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Solution Overview
Problem
Existing semiconductor light-emitting devices struggle to emit a majority of light from the top surface without requiring the removal of the growth substrate, limiting their efficiency and manufacturing processes.
Innovation Solution
A semiconductor structure with a light emitting layer between n-type and p-type regions is attached to a growth substrate with angled sidewalls, where a reflective layer is disposed on the sidewalls to enhance light extraction through the top surface, and a thin growth substrate is used to facilitate efficient light emission without substrate removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light emitting devices are designed to emit light from the top surface only, then light extraction efficiency is improved, but manufacturing complexity increases due to substrate removal requirements
Solution Approach 1:
The growth substrate is designed with asymmetric geometry featuring angled sidewalls instead of vertical walls. This asymmetric shape causes light propagating through the substrate to be redirected toward the top surface at favorable angles for extraction, while preventing light from escaping through the angled side surfaces. The asymmetric geometry thus achieves top-emission without requiring substrate removal.
Solution Approach 2:
The angled sidewalls of the growth substrate, which could potentially cause light loss through side emission, are instead designed to reflect light back toward the top surface. The angled geometry converts what would be harmful light leakage into beneficial light redirection, improving top surface extraction efficiency without requiring complex substrate removal processes.
2Loss of energy
If the growth substrate is made thinner to improve light extraction, then light transmission is improved, but mechanical strength decreases
Solution Approach 1:
The substrate maintains a relatively thick central region for mechanical strength while featuring angled sidewalls that create effective light extraction paths. The asymmetric geometry allows light to be redirected at the angled interfaces, achieving efficient extraction without requiring the entire substrate to be made thin, thus preserving mechanical integrity.
Solution Approach 2:
Instead of reducing substrate thickness uniformly in one dimension, the solution introduces angular geometry in multiple dimensions. The angled sidewalls create three-dimensional light redirection paths that achieve efficient extraction without compromising the substrate's overall thickness and mechanical strength.
3Loss of energy
If reflective material is applied to side surfaces to prevent light loss, then light extraction through top surface is improved, but manufacturing complexity increases
Solution Approach 1:
The angled sidewalls themselves function as passive optical elements that redirect light toward the top surface through geometric optics rather than requiring additional reflective coatings. This geometric solution achieves the light redirection function that would otherwise require complex manufacturing steps to apply reflective materials, thereby reducing manufacturing complexity while improving 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 allows for a significant increase in light extraction through the top surface, improving the efficiency of semiconductor light-emitting devices while eliminating the need for substrate removal, thus simplifying the manufacturing process and enhancing device performance.
Implementation Method 1
A reflective layer is disposed on the angled sidewall
Data Source
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AI summary
Embodiments of the invention include a semiconductor structure including a light emitting layer sandwiched between an n-type region and a p-type region. A growth substrate is attached to the semiconductor structure. The growth substrate has at least one angled sidewall. A reflective layer is disposed on the angled sidewall. A majority of light extracted from the semiconductor structure and the growth substrate is extracted through a first surface of the growth substrate.