UVC Nanowire Emitter Structure for Higher Quantum Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
UVC LED devices face challenges with low wall plug efficiency and poor external quantum efficiency, particularly for wavelengths shorter than 250 nm, due to non-radiative recombination centers, weak dipole moments, and transverse-magnetic mode polarized emission, which limits their commercial availability and effectiveness.
Innovation Solution
The development of a light emitting device using selective area epitaxial growth of AlGaN quantum wells on n+ doped nanostructures, which diverts defect propagation, provides a non-polar surface, and angles transverse magnetic polarized emission to improve emission efficiency, comprising a substrate with patterned mask regions, nanostructures, and conformal p-doped layers to form an emitter tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nanometer scale selective-area epitaxy with circular apertures is used to grow vertically oriented nanowires, then internal quantum efficiency is improved, but external quantum efficiency deteriorates due to reduced area fraction of the emitter layer
Solution Approach 1:
The patent transitions from two-dimensional planar emitters to three-dimensional vertically oriented nanowire structures. This dimensional change allows the emitter to extend in the vertical dimension while maintaining a compact footprint, thereby increasing the effective emitter area fraction without compromising the selective-area growth benefits for internal quantum efficiency
Solution Approach 2:
The patent implements a core-shell structure where the nanowire core is nested within a shell layer. This nested configuration increases the effective emitter area by providing multiple emission interfaces (core surface and shell outer surface) while maintaining the compact nanowire footprint, thus resolving the contradiction between internal and external quantum efficiency
2Illumination intensity
If AlGaN is grown on the side walls of GaN vertical fins via dry etching, then TM polarized light extraction is improved, but surface damage occurs requiring additional wet-etch steps
Solution Approach 1:
The patent extracts the harmful dry-etching step from the manufacturing process by directly growing nanowires on patterned substrates without requiring fin formation through dry etching. This eliminates surface damage while maintaining the vertical orientation needed for TM polarized light extraction
Solution Approach 2:
The patent introduces a patterned substrate with circular apertures as an intermediary element that guides nanowire growth in vertical orientations. This intermediary structure achieves the desired vertical fin-like morphology without the damaging dry-etching process, thereby improving TM polarized light extraction while avoiding surface damage
3Illumination intensity
If InGaN is used as active material, then visible spectrum emission is achieved, but UVC range emission is not obtained
Solution Approach 1:
The patent changes the material composition parameter by substituting InGaN with AlGaN, which has different bandgap properties. This parameter change enables the active layer to emit in the UVC range (200-280 nm) while maintaining the nanowire structure's optical extraction benefits, thus achieving adaptability for UVC applications
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 the external quantum efficiency and internal efficiency of UVC LED devices, allowing for more efficient emission in the 200-350 nm range, addressing issues of non-radiative recombination and polarized emission, and enabling broader commercial applications including sanitization and lighting.
Implementation Method 1
low wall plug efficiency. Prior experimental UVC LED devices also have disadvantages with respect to poor external quantum efficiency. This is particularly true for LEDs emitting wavelengths shorter than 250 nm
Implementation Method 2
An active layer is disposed over the plurality of nanostructures. The active layer is a quantum well structure and comprises at least one material chosen from AlN, AlGaN and GaN
Implementation Method 3
Both the active layer and the p-doped layer are conformal to the plurality of nanostructures so as to form an emitter tip over the core tip
Data Source
AI summary
A light emitting device for emitting UVC radiation. The device comprises a substrate and a patterned layer. The patterned layer comprises a plurality of mask regions on the substrate. Exposed portions of the substrate are disposed between the mask regions. A plurality of nanostructures are disposed on the exposed portions of the substrate and over the mask regions, the plurality of nanostructures being a single crystal semiconductor and comprising a core tip. An active layer is disposed over the plurality of nanostructures. The active layer is a quantum well structure and comprises at least one material chosen from AIN, AlGaN and GaN. A p-doped layer is disposed over the active layer. Both the active layer and the p-doped layer are conformal to the plurality of nanostructures so as to form an emitter tip over the core tip.