Cavity-Containing AlN Buffer for DUV LED Stress Relief
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Solution Overview
Problem
The growth of high-quality AlN buffer layers on substrates like sapphire, silicon carbide, and silicon for deep ultraviolet light emitting diodes (DUV LEDs) is challenging due to high dislocation density and cracking issues, which affects the efficiency of DUV LEDs.
Innovation Solution
A semiconductor structure with a cavity-containing layer grown at a higher V/III ratio and variable temperature schedule, allowing for controlled cavity size and density, reducing internal stresses and dislocations, and enabling uniform composition in group III nitride-based semiconductor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional epitaxial growth is used to grow AlN buffer layers on sapphire, silicon carbide, or silicon substrates, then the semiconductor layers can be formed, but high dislocation density and cracking occur due to stress accumulation
Solution Approach 1:
The patent applies segmentation by introducing a patterned buffer layer with periodic structures (ridges and grooves) instead of a continuous layer. This segmentation breaks up the stress distribution and dislocation propagation paths, reducing overall dislocation density in the overgrown semiconductor layer while maintaining structural integrity for device fabrication.
Solution Approach 2:
The patent implements local quality by creating regions with different buffer layer thicknesses and compositions - thicker regions under active areas and thinner or patterned regions in other areas. This local variation optimizes stress management and dislocation control specifically where needed, improving reliability without compromising overall manufacturability.
2Reliability
If thick AlGaN epitaxial layers are grown to reduce current crowding in DUV LEDs, then device performance improves, but stress accumulation increases leading to cracking
Solution Approach 1:
The patterned buffer layer segments the stress distribution throughout the thick AlGaN epitaxial layer. The periodic ridge and groove structure creates stress relief zones that prevent crack propagation, enabling the growth of thick layers needed for current crowding reduction while maintaining crack resistance.
Solution Approach 2:
The patterned buffer layer acts as an intermediary between the substrate and the thick AlGaN epitaxial layer. It mediates the stress transfer, absorbing and redistributing mechanical stress to prevent cracking in the thick overgrown layer while still supporting the necessary thickness for device performance.
3Reliability
If microchannel epitaxy is used to reduce stress accumulation, then dislocation density decreases, but the process complexity increases due to mask patterning requirements
Solution Approach 1:
The patent applies self-service by using self-aligned patterning techniques where the buffer layer pattern is formed through processes that automatically align with subsequent growth steps. This reduces the need for multiple separate mask alignment steps, lowering process complexity while maintaining the stress reduction benefits of the patterned structure.
4Stress or pressure
If superlattice structures are grown to control tensile and compressive stresses, then strain mitigation is achieved, but uniform composition control becomes difficult
Solution Approach 1:
The patterned buffer layer enables local quality control by allowing different regions to have optimized compositions and thicknesses. This local optimization maintains stress control benefits while achieving better overall composition uniformity compared to uniform superlattice structures, as each region can be tailored to its specific stress requirements.
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 reduces dislocation density and cracking in semiconductor layers, improving the efficiency and quality of DUV LEDs by effectively managing internal stresses and promoting uniform composition.
Implementation Method 1
The residual stress can be released effectively since the overgrown layer easily deforms
Implementation Method 2
epitaxially grown semiconductor layers
Data Source
AI summary
A semiconductor structure, such as a group III nitride-based semiconductor structure is provided. The semiconductor structure includes a cavity containing semiconductor layer. The cavity containing semiconductor layer can have a thickness greater than two monolayers and a multiple cavities. The cavities can have a characteristic size of at least one nanometer and a characteristic separation of at least five nanometers.