Selective AlN Substrate Removal for UV Device Separation
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Solution Overview
Problem
Existing light emitting devices grown on bulk crystalline aluminum nitride (AlN) substrates are inseparable due to the inability to successfully remove the substrate using techniques developed for other substrates, limiting the fabrication of high-bandgap devices that can operate in the 200 to 365 nm wavelength range for applications like water purification and UV curing.
Innovation Solution
The development of chemical processes for selectively etching the nitrogen polar face of the bulk AlN substrate, allowing for the substantial removal or thinning of the substrate, enabling the separation of AlN-grown devices from their native substrate and the epitaxial growth of light emitting layers without the bulk substrate, which can then be used in various device structures or as stand-alone templates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional substrate removal techniques are used, then other substrates can be removed successfully, but bulk crystalline AlN substrates cannot be removed
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and properties of etching solutions to specifically target AlN substrates. By adjusting pH levels, temperature, and chemical concentrations, the etching process achieves selective removal of AlN while preserving the epitaxial layers, resolving the contradiction between removing AlN substrates and maintaining device integrity.
Solution Approach 2:
The patent introduces intermediate chemical agents and processing steps that facilitate the separation between the AlN substrate and epitaxial layers. These intermediaries enable controlled chemical reactions that selectively attack the substrate interface, allowing successful separation where conventional direct removal techniques failed.
2Strength
If the bulk AlN substrate is kept intact, then device structural integrity is maintained, but light extraction is limited and device separation is impossible
Solution Approach 1:
The patent applies segmentation by dividing the device structure into separable components: the epitaxial device layers and the AlN substrate. Through selective chemical etching, the bond between these segments is broken, allowing the device to be separated from the substrate while each component maintains its structural integrity for subsequent processing or application.
Solution Approach 2:
The patent extracts the AlN substrate from the device structure through selective removal processes. This extraction enables the epitaxial layers to be separated and transferred to different substrates or configurations, enhancing device versatility while the removed substrate can be reused or disposed of properly.
3Adaptability or versatility
If the AlN substrate is removed completely, then device separation and light extraction are enhanced, but substrate support is lost
Solution Approach 1:
The patent applies partial action by selectively removing only the AlN substrate portion while leaving the epitaxial device layers intact. This partial removal achieves the goal of device separation and improved light extraction without completely destroying the structural support system, as the epitaxial layers themselves provide sufficient mechanical support for the 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 enables the creation of high-bandgap devices that can emit light through the substrate side, enhance light extraction, and facilitate vertical injection architectures, while maintaining low defect densities and optical transparency, thus overcoming the limitations of previous technologies.
Implementation Method 1
The development of chemical processes for selectively etching the nitrogen polar face of the bulk AlN substrate, allowing for the substantial removal or thinning of the substrate
Implementation Method 2
epitaxial growth of light emitting layers without the bulk substrate
Data Source
AI summary
One or more layers are epitaxially grown on a bulk crystalline AlN substrate. The epitaxial layers include a surface which is the initial surface of epitaxial growth of the epitaxial layers. The AlN substrate is substantially removed over a majority of the initial surface of epitaxial growth.