Epitaxial graphene transistors: enhancing performance via hydrogen intercalation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electrical Engineering

Background:

• The performance of graphene-based electronic devices is often limited by the interface with the substrate.
• The presence of a buffer layer at the graphene/SiC(0001) interface can impede charge carrier transport.
• Optimizing this interface is crucial for realizing high-frequency applications.

Purpose of the Study:

• To directly demonstrate the impact of buffer layer elimination at the graphene/SiC(0001) interface.
• To quantify the improvements in carrier mobility and transistor performance after buffer elimination.
• To assess the high-frequency capabilities of optimized graphene transistors.

Main Methods:

• Graphene synthesis on SiC(0001) with subsequent buffer layer removal.
• Electrical characterization of graphene properties, including carrier mobility.
• Fabrication and testing of graphene field-effect transistors (GFETs).
• Measurement of transistor parameters such as current saturation, transconductance, and current-gain cutoff frequency.

Main Results:

• Carrier mobility increased from 800 cm²/Vs to over 2000 cm²/Vs after buffer elimination.
• Graphene transistor current saturation improved from 750 mA/mm to over 1300 mA/mm.
• Transconductance enhanced from 175 mS/mm to over 400 mS.
• A 10x improvement in extrinsic current gain response was observed.
• Optimal extrinsic current-gain cutoff frequencies reached 24 GHz.

Conclusions:

• Buffer elimination is critical for high-frequency graphene applications on SiC(0001).
• Optimized interfaces lead to substantial improvements in carrier mobility and transistor performance metrics.
• The achieved 24 GHz cutoff frequency highlights the potential of bufferless graphene for advanced electronic devices.