Oxide Epitaxial UV Emitters on LiF Substrates for UVC Output
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Solution Overview
Problem
Ultraviolet light emitting devices (UVLEDs) face efficiency and output power limitations due to low crystallographic structure quality of AlInGaN epitaxially deposited layers, primarily because of the lack of native substrates and significant structural mismatch with sapphire, which restricts UVC operation and reduces optical power as wavelength decreases below 280 nm.
Innovation Solution
The development of an optoelectronic semiconductor light emitting device with a substrate and epitaxial semiconductor layers, where at least one layer comprises a metal oxide such as (AlxGa1−x)2O3, enabling light emission in the range of 150 nm to 425 nm by optimizing the optical emission region band structure and using strain to modify bandgap energies, thereby improving efficiency and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sapphire substrate is used to grow AlInGaN epitaxial layers, then device structure can be formed, but crystallographic structure quality deteriorates due to large lattice mismatch
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the sapphire substrate and the AlInGaN epitaxial layers. This buffer layer serves as a transition medium that reduces the lattice mismatch stress and prevents defect propagation from the sapphire substrate to the active device layers, thereby improving crystallographic structure quality while still allowing use of readily available sapphire substrates.
Solution Approach 2:
The patent modifies the compositional parameters of the epitaxial layers by using AlInGaN with optimized aluminum and indium ratios. By carefully controlling the composition gradient and stoichiometry during epitaxial growth, the patent achieves better lattice matching with the sapphire substrate, reducing structural defects and improving overall crystal quality.
2Manufacturing precision
If AlN is used to improve crystal structure quality, then epitaxial layer quality improves, but UVC operation is limited to approximately 215 nm wavelength
Solution Approach 1:
The patent employs composite AlInGaN material system that combines aluminum nitride (providing good crystal structure) with indium gallium nitride (providing tunable bandgap). This composite approach allows optimization of both crystallographic quality and optical wavelength range, achieving UVC emission at wavelengths longer than 215 nm while maintaining high structural quality.
Solution Approach 2:
The patent changes the compositional parameters by incorporating indium into the AlGaN structure to form AlInGaN. The indium component reduces the bandgap energy, enabling light emission at longer wavelengths within the UVC region (above 215 nm) while the aluminum component maintains the wide bandgap necessary for UV emission and good crystal structure.
3Illumination intensity
If Group-III-Nitride materials are used for UVLED, then UVC light emission is achieved, but output optical power decreases dramatically below 280 nm wavelength
Solution Approach 1:
The patent optimizes the compositional parameters of AlInGaN to achieve the desired wavelength output while maintaining high quantum efficiency. By precisely controlling the aluminum and indium ratios, the patent tunes the bandgap to match target wavelengths in the UVC region, maximizing optical power output at each specific wavelength rather than suffering dramatic declines below 280 nm.
Solution Approach 2:
The patent implements dynamic optimization of the epitaxial layer structure with graded composition profiles. The composition is gradually varied through the layer thickness to manage dislocation density and improve carrier recombination efficiency, thereby maintaining high optical power output across the UVC wavelength range including below 280 nm.
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 enhances the efficiency and output of UVLEDs by reducing defects and extending operational wavelength range, overcoming the limitations of traditional Group-III-Nitride based UVLEDs, particularly in the UVC region.
Implementation Method 1
The optical emission region has an epitaxial metal oxide layer supported by the substrate, where the epitaxial metal oxide layer has an optical emission region band gap energy capable of generating light of the predetermined wavelength
Data Source
AI summary
In some embodiments, an optoelectronic semiconductor light emitting device includes a single crystal LiF substrate and an optical emission region including an epitaxial oxide layer disposed on the substrate. The optical emission region can be configured to emit light having a wavelength in a range from 150 nm to 425 nm. In some embodiments, a semiconductor structure includes a single crystal LiF substrate and an epitaxial oxide layer disposed on the substrate, where the epitaxial layer includes MgxAl2(1−x)O3−2x or MgxGa2(1−x)O3−2x where 0≤x≤1, or a polar form of Ga2O3 with a hexagonal crystal symmetry.