GaN Epitaxy on Graphene-Terminated SiC Substrates
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Solution Overview
Problem
The high cost and limitations of sapphire substrates in manufacturing gallium nitride (GaN)-based semiconductor devices, such as LEDs, due to expensive material costs and low thermal conductivity, which lead to increased device costs and performance degradation.
Innovation Solution
A method for forming epitaxial gallium nitride layers on reusable silicon carbide substrates using a graphene layer and metal monolayer, allowing for the cleavage and transfer of these layers for device fabrication, enabling top and bottom contact configurations and improved thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire substrates are used to fabricate GaN-based devices, then the devices can be manufactured, but the manufacturing cost increases due to expensive sapphire substrates
Solution Approach 1:
The patent uses silicon carbide substrates instead of expensive sapphire substrates. The silicon carbide substrates are cheaper and can be reused after the GaN layers are transferred, eliminating the need for expensive disposable sapphire substrates in each manufacturing cycle.
Solution Approach 2:
The patent introduces a transfer substrate as an intermediary carrier. The GaN layers are first grown on the transfer substrate, then transferred to the final device substrate. This intermediary approach allows the expensive GaN layers to be separated from the substrate material, enabling substrate reuse and reducing overall manufacturing cost.
2Reliability
If sapphire substrates are used for GaN-based devices, then fabrication is enabled, but thermal conductivity is poor leading to heat dissipation issues
Solution Approach 1:
The patent changes the substrate material parameter from sapphire to silicon carbide. Silicon carbide has superior thermal conductivity compared to sapphire, which improves heat dissipation from the GaN layers while maintaining the fabrication capability.
3Reliability
If conventional GaN device fabrication is used, then devices can be manufactured, but current crowding effects occur reducing electrical performance
Solution Approach 1:
The patent transitions from lateral current flow in conventional planar devices to vertical current flow by growing GaN layers in a vertical orientation on the silicon carbide substrate. This vertical architecture eliminates current crowding at lateral contacts and improves electrical performance by providing uniform current distribution throughout the active region.
4Reliability
If GaN epitaxial layers are grown on sapphire substrates, then devices can be fabricated, but the substrates cannot be reused increasing manufacturing cost
Solution Approach 1:
The patent uses a transfer substrate as an intermediary that can be reused. The GaN layers are grown on the transfer substrate, then transferred to the final device substrate. This allows the transfer substrate to be reused multiple times, significantly improving productivity and reducing manufacturing cost compared to single-use sapphire substrates.
Solution Approach 2:
The patent extracts the GaN layers from the substrate through a transfer process. The GaN epitaxial layers are separated from the silicon carbide substrate using a transfer substrate, allowing the substrate to be reused for subsequent batches, thereby eliminating the waste associated with single-use sapphire substrates.
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 reduces manufacturing costs, enhances electrical performance, and extends the lifespan of GaN-based devices by utilizing more affordable and thermally conductive substrates while improving carrier injection and thermal management.
Implementation Method 1
forming a graphene layer on a silicon carbide substrate
Implementation Method 2
depositing a metal containing monolayer on the graphene layer
Implementation Method 3
depositing a metal containing monolayer on the graphene layer
Implementation Method 4
forming an epitaxial gallium nitride layer on the metal containing monolayer
Implementation Method 5
The layered stack of the metal containing monolayer and the epitaxial layer of gallium containing material may be cleaved from the graphene layer
Data Source
AI summary
A method of forming an epitaxial semiconductor material that includes forming a graphene layer on a semiconductor and carbon containing substrate and depositing a metal containing monolayer on the graphene layer. An epitaxial layer of a gallium containing material is formed on the metal containing monolayer. A layered stack of the metal containing monolayer and the epitaxial layer of gallium containing material is cleaved from the graphene layer that is present on the semiconductor and carbon containing substrate.