LiF-Co-Deposited Ga2O3 Epitaxy for Higher-Power UV Emission
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Solution Overview
Problem
Ultraviolet light emitting diodes (UVLEDs) based on Group-III-Nitrides face efficiency and output power limitations due to low crystallographic structure quality and structural mismatch with substrates, particularly in the UVC wavelength region, where the highest bandgap material AlN restricts operation to around 215 nm with a decline in output power below 280 nm.
Innovation Solution
An optoelectronic semiconductor light emitting device with a substrate and epitaxial semiconductor layers comprising metal oxides, such as (AlxGa1-x)2O3, configured to emit light in the range of 150 nm to 425 nm, utilizing epitaxial metal oxide layers with specific bandgap energies and crystal symmetries to enhance optical emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Group-III-Nitride (AlInGaN) compositions are used to generate UVC light, then light emission in the UVC wavelength band is achieved, but crystallographic structure quality deteriorates and output optical power is limited
Solution Approach 1:
The patent changes the material composition parameters by using AlInGaO3 perovskite instead of AlInGaN wurtzite structure, and further optimizes the Al/(In+Ga) ratio parameter to achieve both high crystal quality and efficient UVC emission. This parameter transformation resolves the contradiction by finding optimal compositional parameters that satisfy both structural quality and optical performance requirements.
Solution Approach 2:
The invention employs composite material strategy by creating AlInGaO3 perovskite layers with specific compositional ratios, combining multiple elements (Al, In, Ga, O) in optimized proportions. This composite approach enables simultaneous achievement of high crystallographic quality and efficient UVC light emission, resolving the contradiction between structural quality and optical output.
2Length of moving object
If AlN is used as the highest bandgap material for UVC operation, then operation at wavelengths around 215 nm is achieved, but output optical power dramatically declines below 280 nm
Solution Approach 1:
The patent optimizes the compositional parameter Al/(In+Ga) ratio in the AlInGaO3 perovskite structure to tune the bandgap energy. By controlling this parameter within specific ranges, the material achieves optimal balance between emission wavelength extension and maintained output power, resolving the contradiction between wavelength range and optical power.
3Ease of manufacture
If sapphire (corundum Al2O3) is used as a compromise starting surface crystal, then heteroepitaxial growth is enabled, but structural mismatch creates large density of crystalline defects
Solution Approach 1:
The patent introduces an AlInGaO3 perovskite buffer layer as an intermediary between the sapphire substrate and the active UVC emitting layers. This intermediate layer acts as a transition that reduces the structural mismatch and minimizes the transmission of crystalline defects from the substrate to the active regions, thereby enabling heteroepitaxial growth while maintaining low defect density.
4Illumination intensity
If AlInGaN epitaxial layers are deposited on mismatched substrates, then UVC light emission is achieved, but efficiency is limited by inherent low crystallographic structure quality
Solution Approach 1:
The patent transforms the material system from AlInGaN to AlInGaO3 perovskite with optimized compositional parameters, achieving both UVC emission and high conversion efficiency by eliminating the crystallographic quality issues inherent in the nitride system on mismatched substrates.
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 solution enables improved efficiency and extended operational range for UVLEDs by reducing crystalline defects and increasing output power across the desired wavelength range, overcoming the limitations of traditional Group-III-Nitride based UVLEDs.
Implementation Method 1
Electro-optical conversion of electrical energy into discrete optical wavelengths with extremely high efficiency has generally been achieved using a tailor-made semiconductor having the required properties to achieve the spatial recombination of charge carriers of electrons and holes to emit light of the required wavelength
Implementation Method 2
Each of the epitaxial semiconductor layers comprises a metal oxide... an epitaxial metal oxide layer supported by the substrate
Data Source
AI summary
In some embodiments, a composition of matter includes Li and F atoms within a single crystal Ga2O3 host including a monoclinic, orthorhombic, cubic, corundum, or hexagonal crystal symmetry, or within a single crystal LiGaO2 host including an orthorhombic or trigonal crystal symmetry. In some embodiments, a method includes sublimating a lithium fluoride (LiF) bulk crystal within a Knudsen cell to provide both Li and F and co-depositing the Li and F with an elemental Ga beam under an activated oxygen environment. The method can further include growing, on a growth surface of a substrate, an epitaxial layer including the Li, the F, the Ga, and the activated oxygen within an epitaxially formed Ga2O3 or LiGaO2 host.