Metal Oxide Superlattice LED Structure for Low-Defect UV Emission
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Solution Overview
Problem
Existing UVLEDs face efficiency limitations due to the low crystallographic structure quality of AlInGaN epitaxially deposited layers, primarily because of the lack of native substrates and significant lattice and symmetry mismatches, which restrict UVC operation to approximately 215 nm with a decline in output optical power below 280 nm.
Innovation Solution
Employing a substrate with a single crystal (AlxGa1−x)2O3 symmetry and epitaxial oxide layers, such as (AlyGa1−y)2O3, to create a semiconductor structure that supports light emission from 150 nm to 425 nm by utilizing superlattices and heterojunctions with compatible crystal symmetries, reducing defect density and enhancing optical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sapphire (corundum Al2O3) is used as a substrate to heterogeneously seed Group-III-Nitrides, then light emission in UVC wavelength band is enabled, but crystal lattice and symmetry mismatch creates very large density of crystalline defects that severely reduces efficiency
Solution Approach 1:
The patent introduces an intermediate buffer layer of aluminum oxide (AlOx) with controlled oxygen content between the sapphire substrate and the AlInGaN epitaxial layers. This intermediary layer serves as a transition zone that reduces the crystal lattice and symmetry mismatch, thereby decreasing the density of crystalline defects and improving the overall crystallographic structure quality while enabling efficient UVC light emission
Solution Approach 2:
The patent modifies the oxygen content parameter in the aluminum oxide buffer layer (creating AlOx where x < 1) to optimize the crystallographic matching between the sapphire substrate and the Group-III-Nitride layers. By controlling the oxygen stoichiometry, the buffer layer's lattice parameters can be adjusted to reduce mismatch, thereby improving structural quality and electrical conversion efficiency
2Reliability
If AlN is used as the substrate material to improve crystallographic structure quality, then efficiency is improved, but UVC operation is limited to approximately 215 nm with dramatic decline in output optical power below 280 nm
Solution Approach 1:
The patent employs sapphire (corundum Al2O3) as a universal substrate that can support Group-III-Nitride-based LEDs across a broad wavelength range from 280 nm to 425 nm, rather than being limited to a narrow wavelength range. The sapphire substrate provides both mechanical support and optical transparency across this extended range, enabling multi-wavelength UV emission applications
Solution Approach 2:
The aluminum oxide buffer layer with controlled oxygen content acts as an intermediary that enables the sapphire substrate to support AlInGaN layers for wavelengths below 280 nm while maintaining good crystallographic structure quality, thereby extending the operational wavelength range while preserving efficiency
3Illumination intensity
If Gallium-Indium-Aluminum-Nitride (GaInAlN) compositions are used to achieve UV light emission, then light emission in UVC wavelength band is enabled, but large lattice mismatch with sapphire creates high defect density that reduces output optical power
Solution Approach 1:
The patent introduces an aluminum oxide (AlOx) buffer layer with controlled oxygen content as an intermediary between the sapphire substrate and the GaInAlN epitaxial layers. This buffer layer reduces the lattice mismatch and symmetry mismatch between the substrate and the nitride layers, thereby decreasing the density of crystalline defects and improving output optical power in the UVC wavelength band
Solution Approach 2:
The patent controls the oxygen content parameter in the aluminum oxide buffer layer to optimize the lattice matching. By adjusting the oxygen stoichiometry (AlOx where x < 1), the buffer layer's lattice parameters are tuned to reduce mismatch with both the sapphire substrate and the GaInAlN layers, improving manufacturing precision and reducing defect density
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 proposed solution enables efficient UV light emission across a broader wavelength range (150 nm to 425 nm) by minimizing crystalline defects and optimizing bandgap energy, thereby improving output optical power and efficiency.
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
A semiconductor structure includes a superlattice with two or more unit cells, wherein each of the unit cells includes: a first epitaxial layer including NiO; and a second epitaxial layer including a second epitaxial oxide material. In some cases, the semiconductor structure can include: a first region including p-type conductivity, wherein the first region includes the superlattice; a second region including an epitaxial oxide material; and a third region including an epitaxial oxide material, wherein the second region is located between the first region and the third region along a growth direction.