Crystalline Layer Growth on Amorphous Substrates via Seed Layer
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Solution Overview
Problem
Current methods face challenges in growing high-quality single-crystalline Group III-V nitride layers on amorphous silicon substrates due to lattice mismatch and nitrogen overpressure issues, leading to uncontrolled amorphous SiNx formation and poor layer quality.
Innovation Solution
The use of an ultra-thin seed layer comprising a Group III chalcogenide, such as GaSe, which is annealed in ammonia to form a nanocrystalline GaN layer, allowing for the growth of crystalline layers even on amorphous substrates like SiO2, utilizing methods like hydride vapor phase epitaxy or chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gaseous nitrogen source is used during molecular beam epitaxial growth on silicon substrate, then nitrogen background is present in growth apparatus, but uncontrolled amorphous SiNx layer forms on silicon surface
Solution Approach 1:
The patent applies preliminary action by introducing a controlled nitrogen exposure step before epitaxial growth to intentionally form a uniform amorphous SiNx layer. This pre-formed layer serves as a buffer that prevents uncontrolled SiNx formation during subsequent growth, thereby improving manufacturing precision while maintaining necessary nitrogen background
Solution Approach 2:
The patent utilizes parameter changes by controlling nitrogen background pressure and exposure time to precisely regulate the formation of amorphous SiNx layer. By adjusting these parameters, the method achieves uniform layer formation with controlled thickness, transforming the harmful uncontrolled SiNx formation into a beneficial controlled process
2Reliability
If nitrogen overpressure is applied to avoid film decomposition, then high-quality nitride material is produced, but uncontrolled amorphous SiNx formation occurs on silicon surface
Solution Approach 1:
The patent introduces a preliminary nitrogen exposure step that forms a controlled amorphous SiNx buffer layer before nitride film deposition. This pre-formed buffer layer prevents uncontrolled SiNx formation during high nitrogen overpressure growth, thereby maintaining both film quality and layer uniformity
Solution Approach 2:
The patent uses a controlled amorphous SiNx layer as an intermediary buffer between the silicon substrate and the nitride film. This intermediary layer mediates the interaction between nitrogen overpressure and the substrate, preventing direct uncontrolled reaction while allowing high-quality nitride growth
3Ease of manufacture
If lattice mismatch is present between nitride and silicon substrate, then nitride growth is difficult, but amorphous SiNx layer forms spontaneously
Solution Approach 1:
The patent applies preliminary action by forming a controlled amorphous SiNx buffer layer before nitride deposition. This buffer layer accommodates the lattice mismatch between nitride and silicon, making nitride growth easier while preventing spontaneous uncontrolled SiNx formation
Solution Approach 2:
The patent introduces a controlled amorphous SiNx layer as an intermediary buffer that mediates the lattice mismatch between nitride and silicon substrates. This intermediary enables easier nitride growth by reducing direct lattice conflict while preventing uncontrolled SiNx formation
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 reliable and cost-effective growth of single-crystal or polycrystalline Group III-V films on amorphous substrates, improving layer quality and reducing defects, as demonstrated by the transformation of GaSe to GaN with smoother film formation and fewer interface defects.
Implementation Method 1
annealed in ammonia to form a nanocrystalline GaN layer
Implementation Method 2
the seed layers are formed by a chemical conversion
Implementation Method 3
growing a two-dimensional (2D) layer on a substrate
Implementation Method 4
transforming the one or more seed layers into a thin film
Data Source
AI summary
This disclosure relates to methods of growing crystalline layers on amorphous substrates by way of an ultra-thin seed layer, methods for preparing the seed layer, and compositions comprising both. In an aspect of the invention, the crystalline layers can be thin films. In a preferred embodiment, these thin films can be free-standing.