Core-Shell InGaN/AlGaN Nanowires for Green-Gap Light Emission
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Solution Overview
Problem
Conventional InGaN/GaN light emitters face efficiency and stability issues due to defects, dislocations, and strain-induced polarization fields, particularly in the green and amber wavelength ranges, leading to a 'green gap' in LED and laser technologies.
Innovation Solution
The development of core/shell quantum nanowire photonic structures using Selective Area Growth (SAG) and epitaxial deposition techniques minimizes defects and dislocations, forming InGaN-based light emitters with precise control over size, spacing, and morphology, which suppresses non-radiative recombination and enhances luminescence efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional InGaN/GaN light emitters are used to achieve blue wavelength emission, then efficient operation is achieved, but efficiency and stability degrade considerably with increasing wavelength to the green and amber ranges
Solution Approach 1:
The patent changes the structural parameters of the light emitter by introducing a core-shell nanowire configuration with specific material compositions (InGaN quantum cores surrounded by AlGaN shells). This structural parameter change enables efficient operation across a broader wavelength range including green and amber, resolving the degradation issue of conventional structures.
Solution Approach 2:
The patent employs composite material structure combining InGaN quantum cores with AlGaN shells. This composite approach leverages the advantages of both materials: InGaN for light emission and AlGaN for structural stability and defect reduction, thereby maintaining both efficiency and reliability across different wavelengths.
2Ease of manufacture
If large densities of defects and dislocations are present due to lattice mismatch, then manufacturing is simplified, but quantum efficiency decreases due to small nonradiative lifetime
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the AlGaN shell surrounds and isolates the InGaN quantum core. This local structural modification protects the active emission region from defects while maintaining manufacturing feasibility through selective area growth techniques.
Solution Approach 2:
The AlGaN shell acts as an intermediary layer between the InGaN quantum core and the surrounding environment. It mediates the interaction by providing a protective barrier that reduces the impact of defects and dislocations on the quantum core, thereby preserving quantum efficiency.
3Stability of the object's composition
If strain-induced polarization fields are present, then device structure is maintained, but emission wavelength shifts considerably under high power operation
Solution Approach 1:
The patent changes the strain distribution parameters by introducing the AlGaN shell around the InGaN quantum core. This structural modification alters the stress field configuration, reducing strain-induced polarization effects and thereby stabilizing emission wavelength under high power operation while maintaining structural integrity.
4Ease of manufacture
If conventional top-down etching method is used to fabricate optical cavities, then manufacturing process is established, but large densities of defects and dislocations are inherent
Solution Approach 1:
The patent inverts the conventional fabrication approach by using bottom-up nanowire growth instead of top-down etching. This inversion allows precise control over crystal structure and defect density during the growth process, achieving low defect density while maintaining manufacturing feasibility through established vapor-liquid-solid growth methods.
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 results in highly stable and efficient InGaN-based light emitters with extended band edge modes, achieving uncooled, high-efficiency operation across a broad spectral range, including green and amber wavelengths, and demonstrates enhanced luminescence intensity and reduced spectral broadening.
Implementation Method 1
by exploiting the Purcell effect in an optical microcavity, the radiative lifetime τr can be significantly reduced, thereby leading to an enhancement of the internal quantum efficiency
Implementation Method 2
previously reported GaN optical cavities, including photonic crystals, are generally fabricated from crystalline epilayers using the top-down etching method
Data Source
AI summary
A nanowire can include a first semiconductor portion, a second portion including a quantum structure disposed on the first portion, and a second semiconductor portion disposed on the second portion opposite the first portion. The quantum structure can include one or more quantum core structures and a quantum core shell disposed about the one or more quantum core structures. The one or more quantum core structures can include one or more quantum disks, quantum arch-shaped forms, quantum wells, quantum dots within quantum wells or combinations thereof.