Substrate Fusion for Low-Mismatch Cubic–Non-Cubic Epitaxy
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Solution Overview
Problem
Existing epitaxial techniques are limited by the inability to grow layers on dissimilar crystal-structure substrates, particularly due to poor thermal conductivity and lattice mismatch issues, which restrict the use of materials like Ga2O3 in semiconductor devices.
Innovation Solution
A method is developed to identify low-index crystallographic planes that enable epitaxy on non-cubic materials by selecting parallelogram patterns, such as the β-Ga2O3 β-plane, reducing lattice mismatch to less than 1% with thermally conductive substrates like GaP, and using low-temperature nucleation layers for heteroepitaxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If epitaxial layers are grown on dissimilar crystal-structure substrates, then material diversity and device functionality are increased, but lattice mismatch and thermal conductivity issues arise
Solution Approach 1:
The patent introduces an intermediary substrate layer between the dissimilar crystal structures. Specifically, it uses a cubic substrate (such as silicon or gallium arsenide) as an intermediary to grow the non-cubic beta-Ga2O3 layer. This intermediary approach allows the lattice mismatch to be managed through the intermediate layer, enabling the growth of diverse materials while maintaining structural integrity and reducing direct lattice conflict.
2Ease of manufacture
If commercially-available substrate materials with different crystallographic orientations are used, then ease of manufacture is improved, but manufacturing precision deteriorates due to lattice mismatch
Solution Approach 1:
The patent changes the crystallographic orientation parameters of the substrate to achieve better lattice matching. It specifically identifies and uses particular crystal planes (such as the {110} plane of cubic substrates) that provide optimal lattice matching with the non-cubic material. By selecting specific crystallographic orientations and adjusting growth parameters, the patent achieves low lattice mismatch while using commercially available substrates.
3Manufacturing precision
If low-index crystallographic planes are selected for epitaxy, then manufacturing precision is improved through reduced lattice mismatch, but device complexity increases due to orientation requirements
Solution Approach 1:
The patent exploits the asymmetric properties of specific crystal planes to achieve better lattice matching. By selecting particular low-index planes with specific asymmetric orientations (such as {110} planes at specific angles), the patent creates an asymmetric interface that reduces lattice mismatch. This asymmetric approach allows precise lattice matching while the patent provides guidelines to manage the orientation 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 allows for the growth of diverse materials on dissimilar substrates, enhancing device functionality by overcoming thermal conductivity limitations and enabling the use of materials like Ga2O3 in integrated circuits.
Implementation Method 1
growing epitaxial layers on dissimilar crystal-structure substrates
Implementation Method 2
A lattice mismatch between the cubic material and the non-cubic material is less than about 1%
Implementation Method 3
overcoming thermal conductivity limitations
Data Source
AI summary
Various examples include a substrate and related method for bonding a first substrate formed from a cubic material to a second substrate formed from a non-cubic material. Other examples include a method of finding crystallographic planes of cubic materials being used as epitaxial substrates for non-cubic material epitaxy. By selecting low-index crystallographic planes, the two-dimensional (2D) repetitive pattern appears as parallelograms which enable epitaxy of non-cubic crystals. For example, an appropriate orientation in GaP has been identified as a substrate to the 0-Ga2O3 0-plane. In other embodiments, the disclosed subject-matter describes a method for determining crystallographic planes of cubic materials for bonding a first substrate formed from the cubic material to a second substrate formed from the non-cubic material. Other methods and techniques are also disclosed.