Epitaxial Semiconductor Films on Graphitic Substrates
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Solution Overview
Problem
Conventional semiconductor film growth on substrates of the same material is limiting due to high costs and lattice matching requirements, and heteroepitaxial growth on available substrates is constrained by expensive and scarce materials, with pseudomorphic epilayers facing limitations in thickness and quality due to strain relaxation.
Innovation Solution
The use of graphitic substrates, particularly graphene, for epitaxial growth of semiconductor thin films through molecular beam epitaxy, achieving a lattice match by positioning semiconductor atoms on specific sites on the graphene surface, and optionally using a base layer with minimal lattice mismatch to facilitate growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional homoepitaxial growth is used to ensure lattice matching, then crystal quality is improved, but substrate cost and material availability worsen
Solution Approach 1:
The patent introduces an intermediate layer (such as SiC, GaAs, or AlN) between the conventional substrate and the target semiconductor layer. This intermediary layer serves as a buffer that accommodates lattice mismatch, enabling high-quality epitaxial growth of III-V or II-VI semiconductors on inexpensive silicon substrates without direct lattice matching requirements between the final semiconductor layer and substrate
Solution Approach 2:
The patent replaces expensive and scarce conventional substrates (GaAs, InP) with inexpensive, abundant silicon substrates. The silicon substrate acts as a disposable base that enables cost-effective production of high-quality semiconductor films through the intermediary layer approach
2Ease of manufacture
If heteroepitaxial growth is used to reduce substrate cost, then substrate availability is improved, but lattice mismatch and strain worsen
Solution Approach 1:
The patent uses an intermediary layer with intermediate lattice constant between the silicon substrate and the target III-V or II-VI semiconductor layer. This intermediary layer gradually transitions the lattice constant, reducing the abrupt mismatch and minimizing strain and dislocation formation in the final semiconductor layer
Solution Approach 2:
The patent employs graded buffering layers where the composition is gradually changed from pure silicon at the substrate interface to the target semiconductor composition at the top interface. This gradual parameter change in lattice constant reduces strain accumulation and enables thicker, higher-quality films
3Manufacturing precision
If pseudomorphic epilayers are grown to achieve thin film quality, then film quality is improved, but film thickness is limited due to strain relaxation
Solution Approach 1:
The patent introduces a buffering layer structure that acts as an intermediary between the substrate and the pseudomorphic epilayer. This buffering layer absorbs the strain energy and dislocations, allowing the subsequent pseudomorphic epilayer to be grown much thicker without relaxation, as the strain is already accommodated in the buffer layer
Solution Approach 2:
The patent divides the film structure into multiple segments: a graded buffering layer segment that handles strain accommodation, and a separate pseudomorphic epilayer segment that achieves high quality. This segmentation allows each layer to optimize its function without being constrained by the other's limitations
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 allows for the cost-effective growth of high-quality, thick semiconductor films with minimal strain, enabling a wide range of applications by overcoming the limitations of traditional substrate materials and lattice matching constraints.
Implementation Method 1
a film having been grown epitaxially on said substrate
Implementation Method 2
the invention employs molecular beam epitaxy techniques to grow semiconducting thin films epitaxially on graphitic substrates
Implementation Method 3
with only very weak van der Waals forces holding one layer of the crystal structure to the next layer
Data Source
AI summary
A composition of matter comprising a film on a graphitic substrate, said film having been grown epitaxially on said substrate, wherein said film comprises at least one group III-V compound or at least one group II-VI compound.