Non-C-Plane AlGaInN UV Emitters for Deep UV Extraction
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Solution Overview
Problem
UV emitting devices grown on c-plane substrates face significant efficiency drops as emission wavelength shortens below 250 nm due to transverse-magnetic polarization, making it difficult to extract UV radiation, and challenges persist with p-type conductivity materials for high band gap UV emitters.
Innovation Solution
The use of non-c-plane oriented AlGaN or AlGaInN quantum well structures grown on semi-polar substrates, combined with electron beam excitation to enhance UV radiation extraction and reduce light absorption losses, facilitates the generation of UV radiation with wavelengths less than 250 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If c-plane substrates are used for UV emitting devices, then conventional fabrication is easier, but UV radiation extraction efficiency drops significantly below 250 nm due to transverse-magnetic polarization
Solution Approach 1:
The patent changes the crystallographic orientation parameter from conventional c-plane to non-c-plane (such as m-plane, a-plane, or semi-polar planes) to alter the polarization characteristics of UV emission. This parameter change enables efficient extraction of UV radiation below 250 nm by avoiding transverse-magnetic polarization limitations while maintaining compatibility with standard fabrication processes
Solution Approach 2:
The patent employs composite heterostructure materials consisting of multiple layers with different AlGaN compositions (varying Al content) grown on non-c-plane substrates. This composite structure optimizes both the bandgap for deep UV emission and the crystal orientation for reduced polarization losses, achieving high extraction efficiency at wavelengths below 250 nm
2Device complexity
If p-type conductivity materials are used for high band gap UV emitters, then device structure is simplified, but light absorption losses increase
Solution Approach 1:
The patent changes the material composition parameter by using AlGaN layers with high aluminum content (greater than 50% Al) which inherently exhibit reduced light absorption in the deep UV range. This compositional parameter change allows the use of p-type materials without significant absorption losses, simplifying device structure while maintaining low energy loss
Solution Approach 2:
The patent applies local quality optimization by designing specific AlGaN layers with tailored aluminum compositions in different regions of the heterostructure. The active region uses high-Al content to minimize absorption, while other regions are optimized for carrier injection and electrical conductivity, thereby reducing overall light absorption losses without compromising device functionality
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 significantly enhances the efficiency of UV radiation extraction and reduces light absorption losses, enabling high-quality UV emission with improved carrier injection and reduced voltage requirements for UV emitters.
Implementation Method 1
The active region is configured to generate UV radiation in response to excitation by an electron beam from an electron beam pump source
Implementation Method 2
Some embodiments are directed to a device that emits ultraviolet (UV) radiation through spontaneous emission
Implementation Method 3
Some embodiments are directed to a device that emits ultraviolet (UV) radiation through stimulated emission
Implementation Method 4
The active region is configured to generate UV radiation in response to pumping by an electron beam
Implementation Method 5
The use of non-c-plane oriented AlGaN or AlGaInN quantum well structures grown on semi-polar substrates, combined with electron beam excitation to enhance UV radiation extraction and reduce light absorption losses
Data Source
AI summary
An ultraviolet (UV) radiation emitting device includes an epitaxial heterostructure comprising an AlGaInN active region. The AlGaInN active region includes one or more quantum well structures with Al content greater than about 50% and having a non-c-plane crystallographic growth orientation. The AlGaInN active region is configured to generate UV radiation in response to excitation by an electron beam generated by an electron beam pump source.