Cavity-Containing AlN Buffer Layers for Stress and Crack Relief
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Solution Overview
Problem
The challenge lies in growing high-quality AlN buffer layers on common substrates like sapphire, silicon carbide, and silicon for deep ultraviolet light emitting diodes (DUV LEDs), as existing methods struggle with high dislocation density and cracking issues, which affect the efficiency of these devices.
Innovation Solution
A growth technology that employs a higher V/III ratio and variable temperature schedule to control cavity size and density in the nucleation and semiconductor layers, resulting in a semiconductor structure with reduced internal stresses, threading dislocations, and cracks, using a cavity containing layer with well-separated cavities that differ morphologically from previous porous AlN layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional epitaxial growth methods are used to grow AlN buffer layers on sapphire, silicon carbide, or silicon substrates, then the semiconductor layers can be formed, but the dislocation density remains high and cracking occurs, reducing device efficiency
Solution Approach 1:
The patent applies segmentation by introducing a patterned mask layer with microchannels that divides the growth area into discrete regions. This segmentation prevents dislocation propagation across the entire substrate by confining crystal growth to isolated microchannel regions, thereby reducing overall dislocation density in the semiconductor layer while maintaining structural integrity and preventing cracking
Solution Approach 2:
The patent uses an intermediary approach by introducing a mask layer as a mediator between the substrate and the semiconductor layer. This mask layer with microchannels acts as an intermediate structure that filters out dislocations from the substrate while allowing controlled crystal growth, thus reducing harmful dislocation density and preventing cracking in the final semiconductor layer
2Object-affected harmful factors
If microchannel epitaxy (MCE) is used to reduce stress accumulation, then dislocation density can be reduced, but the process complexity increases due to mask application and patterning requirements
Solution Approach 1:
The patent applies self-service by designing a mask layer that automatically performs multiple functions: it defines microchannel patterns, controls crystal growth directions, and filters dislocations simultaneously. The mask structure is designed to self-organize the epitaxial growth process, eliminating the need for separate complex patterning steps while maintaining effective dislocation reduction
3Stress or pressure
If superlattice structures are grown to mitigate strain differences, then stress control is improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent applies parameter changes by modifying the growth conditions (temperature, pressure, composition ratios) during epitaxial growth to control stress distribution. By adjusting these parameters, the method achieves effective stress mitigation without requiring complex superlattice structures, thereby simplifying the manufacturing process while maintaining stress control
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 internal stresses, leading to improved crystal quality and reduced cracking in semiconductor layers, enhancing the efficiency of DUV LEDs by allowing for uniform composition and stress control in epitaxial growth.
Implementation Method 1
The cavity containing semiconductor layer can be configured to reduce internal stresses, threading dislocations, and cracks in the semiconductor layers
Implementation Method 2
Each of the semiconductor layers can be epitaxially grown on the substrate
Data Source
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Figure 5~6A
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.