Nanowire LED with Non-Uniform InGaN Shell
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Solution Overview
Problem
Conventional planar LED technology faces challenges in fabricating light emitting diodes in the infra-red to green wavelength region due to miscibility gaps and high defect densities in InGaN materials, resulting in lower efficiency compared to blue LEDs.
Innovation Solution
A nanowire LED device with a semiconductor nanowire core and an In(Al)GaN active region quantum well shell having a non-uniform surface profile with indium rich regions, which reduces defects and enhances emission efficiency in the green to red spectral region by self-assembly during shell formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional planar technology is used to fabricate InGaN LEDs in the infra-red to green wavelength region, then the device can be manufactured with existing processes, but the efficiency is much lower than blue color emitting LEDs due to miscibility gaps and high defect densities
Solution Approach 1:
The patent changes the structural parameters of the LED from planar to nanowire configuration, and introduces non-uniform indium composition distribution (indium rich regions with at least 5 atomic percent higher indium content than indium poor regions). This parameter change allows the device to overcome miscibility gaps and reduce defect densities while maintaining manufacturability
Solution Approach 2:
The active region shell is designed with non-uniform indium composition, creating indium rich regions and indium poor regions within the same shell. This local quality variation enables different regions to emit at different wavelengths and reduces overall defect density by avoiding uniform high indium content throughout the entire structure
2Ease of manufacture
If uniform InGaN material composition is used in the active region, then the fabrication process is simpler, but miscibility gaps occur in the red and green wavelength region leading to high defect densities
Solution Approach 1:
The active region shell incorporates spatially varying indium composition with indium rich regions (at least 5 atomic percent higher indium content) and indium poor regions. This local quality variation resolves miscibility gaps by preventing uniform high indium content that causes defects, while still enabling green to red spectral emission
Solution Approach 2:
The patent creates a composite In(Al)GaN active region shell structure with non-uniform composition, combining indium rich and indium poor regions within a single shell. This composite approach allows fabrication with modified processes while achieving precise control over wavelength emission and defect reduction
3Reliability
If the active region shell has a non-uniform surface profile with indium rich regions, then defects are reduced and emission efficiency is enhanced in the green to red spectral region, but the fabrication process becomes more complex
Solution Approach 1:
The patent introduces non-uniform surface profile parameters with peaks and valleys in the active region shell, and varies indium composition (at least 5 atomic percent difference) to create indium rich regions. These parameter changes reduce defects and enhance green to red emission efficiency while maintaining a manageable nanowire-based fabrication approach
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 non-uniform surface profile of the active region shell in the nanowire LED device reduces defects, allowing for high brightness and efficiency in the green to red spectral region, overcoming the limitations of conventional planar technology.
Implementation Method 1
an In(Al)GaN active region quantum well shell located radially around the semiconductor nanowire core. In one embodiment, the active quantum well shell contains indium rich regions having at least 5 atomic percent higher indium content than indium poor regions in the same shell
Data Source
AI summary
A light emitting diode (LED) device includes a semiconductor nanowire core, and an In(Al)GaN active region quantum well shell located radially around the semiconductor nanowire core. The active quantum well shell contains indium rich regions having at least 5 atomic percent higher indium content than indium poor regions in the same shell. The active region quantum well shell has a non-uniform surface profile having at least 3 peaks. Each of the at least 3 peaks is separated from an adjacent one of the at least 3 peaks by a valley, and each of the at least 3 peaks extends at least 2 nm in a radial direction away from an adjacent valley.