Vertical Multi-Junction LED Current Density Management
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Solution Overview
Problem
Current III-nitride LEDs experience a drop in internal quantum efficiency and reliability issues when operated at high current density, leading to reduced efficiency and heat generation.
Innovation Solution
A vertical multi-junction LED structure is created by stacking multiple III-V semiconductor structures with bonding layers to reduce current density and distribute optical output, using conductive and reflective contacts to manage current and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If drive current is increased to produce more photons, then optical output is improved, but internal quantum efficiency drops due to high current density
Solution Approach 1:
The patent divides a single high-current-density LED junction into multiple stacked LED junctions, each operating at lower current density. This segmentation allows the total optical output to be distributed across multiple junctions, maintaining high overall output while preserving the internal quantum efficiency of each individual junction.
Solution Approach 2:
The patent transitions from a planar single-junction LED structure to a vertical multi-junction stacked structure. By stacking LED junctions vertically in multiple layers, the current density is distributed across multiple junctions rather than concentrated in a single plane, effectively reducing the current density per junction while maintaining or increasing total optical output.
2Illumination intensity
If drive current is increased to produce more photons, then optical output is improved, but heat generation increases reducing efficiency
Solution Approach 1:
By segmenting the high-current operation into multiple lower-current junctions stacked vertically, the heat generation is distributed across multiple junctions rather than concentrated in one. This reduces the thermal load per junction, improving heat dissipation and maintaining efficiency.
Solution Approach 2:
The vertical stacking architecture provides additional thermal management dimensions. Heat can be dissipated through multiple junction interfaces and the extended vertical structure, improving thermal conductivity and reducing peak temperatures compared to a single-planar junction.
3Illumination intensity
If drive current is increased to produce more photons, then optical output is improved, but reliability problems occur
Solution Approach 1:
The patent segments the high-stress operation into multiple lower-stress junctions. Each junction operates at reduced current density, which reduces electromigration, junction degradation, and other reliability issues associated with high current density, thereby improving overall device reliability while maintaining high optical output.
Solution Approach 2:
The vertical multi-junction structure distributes electrical and thermal stress across multiple interfaces and layers, reducing the stress concentration on any single junction. This dimensional distribution improves reliability by preventing localized failure modes.
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 reduced current density in each LED junction, enhancing efficiency and reliability by distributing the current and light emission effectively, while maintaining optical output per unit area.
Implementation Method 1
A bonding structure is disposed between the first and second III-V semiconductor structures
Implementation Method 2
A semiconductor light emitting diode (LED) is a semiconductor p-n junction that emits light when forward biased. When an LED is forward biased, electrons generated in an n-type region combine with holes generated in a p-type region, releasing energy in the form of photons
Implementation Method 3
A surface of conductive structure 14 in contact with first LED 20 may be reflective, such that emitted light is directed toward the top surface 32
Data Source
AI summary
An embodiment of the invention comprises a first III-V semiconductor structure including a first light emitting layer disposed between a first n-type region and a first p-type region, and a second III-V semiconductor structure including a second light emitting layer disposed between a second n-type region and a second p-type region. A first contact is formed on a top surface of the first III-V semiconductor structure. A second contact is formed on a bottom surface of the second III-V semiconductor structure. A bonding structure is disposed between the first and second III-V semiconductor structures.