LED Chip Antireflective Films for Higher Light Extraction
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Solution Overview
Problem
Existing LED devices face challenges in achieving high light emission efficiency due to internal reflection, which limits the extraction of light emitted by the active region and reduces external quantum efficiency.
Innovation Solution
Integration of antireflective structures within LED chip structures, including antireflective layers positioned between epitaxially grown active LED structures and carrier substrates, to reduce internal reflections and enhance light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED structures without antireflective layers are used, then the device complexity is low, but the light extraction efficiency is limited due to internal reflections
Solution Approach 1:
An antireflective structure is introduced as an intermediary layer between the active LED structure and the substrate. This intermediate layer reduces internal reflections at the interface, improving light extraction efficiency without significantly complicating the manufacturing process
Solution Approach 2:
The antireflective structure comprises multiple layers with different refractive indices (e.g., first antireflective layer with index n1, second antireflective layer with index n2 where n1 < n2). This composite material approach creates a gradient that progressively reduces reflections, enhancing light extraction while maintaining manufacturing feasibility
2Loss of energy
If antireflective structures are integrated within LED chip structures, then light extraction efficiency is improved, but the device complexity increases
Solution Approach 1:
The antireflective structure is integrated within the existing LED chip structure rather than being added as a separate component. The bonding layer serves dual purposes: providing mechanical bonding between substrates and acting as part of the antireflective structure, thereby reducing overall device complexity
Solution Approach 2:
The bonding layer performs multiple functions: it provides mechanical support, enables substrate removal, and contributes to light extraction by serving as part of the antireflective structure. This multi-functionality reduces the need for additional dedicated components
3Loss of energy
If multiple antireflective layers with different refractive indices are used, then light extraction is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The refractive index parameter is varied across different layers of the antireflective structure to optimize light extraction. By creating a gradient of refractive indices from the substrate interface toward the active LED structure, the patent achieves progressive reduction of internal reflections while using standard manufacturing techniques
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 implementation of antireflective structures in LED chips significantly improves light extraction and external quantum efficiency by minimizing internal reflections, thereby enhancing the overall brightness and emission characteristics of LEDs.
Implementation Method 1
Light extraction and external quantum efficiency of an LED can be limited by a number of factors, including internal reflection
Implementation Method 2
a composition of the single antireflective layer is graded such that an index of refraction of the single antireflective layer is graded between the bonding layer and the substrate
Data Source
AI summary
Light-emitting diode (LED) chips and, more particularly, LED chips with light extraction films and related methods are disclosed. Light extraction films include antireflective structures that are integrated within LED chip structures. Antireflective structures include one or more antireflective layers positioned to reduce internal reflections at various internal interfaces of LED chips. Certain LED chip structures include antireflective structures positioned between epitaxially grown active LED structures and carrier substrates on which the active LED structures are supported. Wafer level bonding sequences with one or more bonding layers are disclosed that facilitate integration of antireflective structures within LED chip structures.