Nanowire LED Axial Radial Injection High Current Density
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Solution Overview
Problem
Current LED technologies face limitations in achieving high current density with high internal quantum efficiency and wavelength flexibility due to issues like droop efficiency, carrier injection difficulties, and the need for electric blocking layers, which restrict the volume of active material and efficiency.
Innovation Solution
The development of nanowire-based optoelectronic devices with axial and radial injection mechanisms, utilizing unintentionally doped nanowires and doped semiconductor materials for electron and hole injection, along with a heterojunction for carrier confinement, increases the active volume and improves quantum efficiency while allowing for wider wavelength selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If planar LED technology with quantum wells is used, then light emission is achieved, but internal quantum efficiency decreases at high current densities due to droop efficiency
Solution Approach 1:
The patent transitions from planar 2D quantum well structures to three-dimensional nanowire structures. This dimensional change enables a fundamental restructuring of the active region where carriers are confined radially while allowing axial current flow, thereby reducing carrier density at any given point and mitigating Auger recombination losses that cause droop efficiency at high current densities.
Solution Approach 2:
The patent divides the active region into multiple discrete nanowires rather than using a continuous planar layer. Each nanowire acts as an independent emission channel with its own quantum confinement, allowing the total current to be distributed across many segments. This segmentation reduces the carrier density in each individual nanowire, maintaining high internal quantum efficiency even at high overall current densities.
2Reliability
If electric blocking layers are added to confine carriers, then radiative recombination is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts and eliminates the AlGaN electron blocking layer from the traditional planar LED structure. Instead of adding blocking layers to confine carriers, the invention uses the inherent radial heterostructure of the nanowire core-shell configuration, where the wider bandgap shell material provides natural carrier confinement without requiring additional blocking layers, thereby simplifying the overall device structure.
Solution Approach 2:
The nanowire structure provides self-confinement through its radial heterostructure. The wider bandgap shell automatically confines both electrons and holes within the narrower bandgap core region through band offset, eliminating the need for external blocking layers. The structure serves its own confinement function inherently, reducing manufacturing complexity.
3Reliability
If multi-quantum wells are used for carrier confinement, then radiative recombination efficiency is improved, but the volume of active material is reduced
Solution Approach 1:
The patent replaces the planar 2D quantum well configuration with three-dimensional nanowire structures. This dimensional transition allows the active material to extend axially along the nanowire length while maintaining radial quantum confinement, effectively increasing the volumetric density of active material compared to planar quantum wells of equivalent lateral dimensions.
Solution Approach 2:
The patent implements a core-shell nanowire structure where the active region is nested within the wider bandgap shell. This nested configuration maximizes the volume of active material by allowing the core to extend fully along the nanowire axis while being radially confined, effectively packing more active material into the available space compared to planar quantum well structures.
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 enhances internal quantum efficiency and allows for higher current densities without droop efficiency losses, expanding the range of achievable wavelengths from red to blue and enabling white light emission.
Implementation Method 1
electrons injected into active layer 16 by means of n layer 12 and holes injected into active layer 16 by means of p layer 24 at least partly radiatively recombine in active layer 16
Implementation Method 2
the quantum multi-wells having a confinement function
Implementation Method 3
EBL layer 22 is necessary to locate radiative recombinations of electron-hole pairs in the InGaN/GaN quantum wells
Data Source
AI summary
A light-emitting diode is provided, including an active semiconductor area for the radiative recombination of electron-hole pairs having a plurality of nanowires, each made of an unintentionally doped semiconductor material, a first semiconductor area for radially injecting holes into each nanowire, the first semiconductor area being made of a doped semiconductor material having a first conductivity type and having a bandgap that is greater than the bandgap of the semiconductor material of the nanowires, and a second semiconductor area for axially injecting electrons into each nanowire, the second semiconductor area being made of a doped semiconductor material having a second conductivity type that is opposite to that of the first conductivity type.