Stacked Infrared LED Tunnel Junction for Higher Optical Output
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Solution Overview
Problem
Infrared LED elements with a peak emission wavelength of 1000 nm or more face challenges in achieving high optical output due to the limited choices of semiconductor materials that can be lattice-matched to InP substrates, leading to inferior light-emitting efficiency and increased costs when trying to enhance output by arranging multiple LED elements.
Innovation Solution
The design includes a multilayer structure with a tunnel junction configuration, utilizing multiple light-emitting layers laminated in a specific direction, where the tunnel layers are made of materials lattice-matched to InP, such as InP, GalnAsP, and AlGalnAs, to improve optical output while minimizing voltage drop and preventing light absorption, allowing for higher efficiency and reduced forward voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple LED elements are arranged to increase output, then optical output increases, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple light-emitting layers within a single LED element structure, merging their light output functions. The multiple LED laminates with respective light-emitting layers are integrated into one device, achieving the effect of multiple elements while maintaining a single manufacturable unit, thus increasing optical output without proportionally increasing manufacturing cost
Solution Approach 2:
The patent transitions from arranging multiple LED elements laterally (horizontal arrangement) to stacking multiple light-emitting layers vertically (vertical arrangement through lamination). This dimensional change allows multiple light-emitting functions to be combined within a compact structure, achieving higher output per element without increasing the horizontal footprint or manufacturing complexity
2Power
If amount of injected electric current is increased to improve output, then optical output increases, but light-emitting efficiency decreases
Solution Approach 1:
The patent divides the light-emitting function into multiple separate light-emitting layers, each operating at optimized current levels. This segmentation allows the total current to be distributed across multiple layers, preventing any single layer from operating in the inefficient high-current regime while maintaining high total optical output
Solution Approach 2:
The patent changes the structural parameter by introducing multiple light-emitting layers with different band gap energies, allowing each layer to operate at optimized injection current levels. This parameter change enables the system to maintain high light-emitting efficiency across a wider range of total current levels compared to a single-layer structure
3Ease of manufacture
If tunnel layers are made of materials lattice-matched to InP, then manufacturing feasibility improves, but light absorption may occur
Solution Approach 1:
The patent changes the material composition parameters of the tunnel layers by using InP-based materials with specific band gap energies that are higher than the emission wavelengths of the light-emitting layers. This parameter change ensures that while the materials are lattice-matched to InP substrates for manufacturing feasibility, their higher band gaps prevent absorption of the emitted infrared light
Solution Approach 2:
The patent employs composite material design where tunnel layers are constructed from InP-based semiconductor materials that combine the properties of lattice matching with InP substrates and appropriate optical transparency. This composite approach allows simultaneous achievement of manufacturing feasibility and minimal light absorption
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 configuration significantly enhances optical output per LED element without significant voltage increase, improving light extraction and reducing costs by using materials that can be lattice-matched to InP substrates, achieving improved performance for infrared LED elements.
Implementation Method 1
a tunnel junction configuration, utilizing multiple light-emitting layers laminated in a specific direction, where the tunnel layers are made of materials lattice-matched to InP
Implementation Method 2
a first light-emitting layer disposed directly or indirectly on top of the first cladding layer, and a second light-emitting layer directly or indirectly disposed on top of the third cladding layer
Data Source
AI summary
The infrared LED element includes a first LED laminate including a first cladding layer of a first conductivity type, a first light-emitting layer, and a second cladding layer of a second conductivity type; a laminate for tunnel junction disposed directly or indirectly on top of the first LED laminate; and a second LED laminate disposed directly or indirectly on top of the laminate for tunnel junction and including a third cladding layer of a first conductivity type, a second light-emitting layer, and a fourth cladding layer of a second conductivity type. The laminate for tunnel junction includes a first tunnel layer containing a second conductivity-type dopant at a higher concentration than the second cladding layer; and a second tunnel layer containing a first conductivity-type dopant at a higher concentration than the third cladding layer and forming a tunnel junction with the first tunnel layer.