High-Velocity Saturation in Graphene Encapsulated by Hexagonal Boron Nitride

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene exhibits exceptional electronic properties, including high carrier mobility.
• Encapsulation with hexagonal boron nitride (hBN) is known to improve graphene quality by reducing substrate interactions.
• Understanding carrier transport dynamics, such as drift velocity, is crucial for electronic device applications.

Purpose of the Study:

• To measure the drift velocity in monolayer graphene encapsulated by hBN.
• To investigate the dependence of drift velocity on carrier density and temperature.
• To compare the observed drift velocities with theoretical models and other graphene systems.

Main Methods:

• Fabrication of monolayer graphene encapsulated by hBN.
• Electrical transport measurements to determine carrier density and mobility.
• Application of varying electric fields to measure drift velocity saturation.
• Comparison with a canonical drift velocity model.

Main Results:

• High carrier mobility exceeding 5 × 10⁴ cm²/V/s was achieved at room temperature.
• Drift velocity saturation was observed at low electric fields (∼0.1 V/μm).
• Room-temperature electron saturation velocities ranged from 6 × 10⁷ cm/s (8 × 10¹¹ cm^-2) to 2.7 × 10⁷ cm/s (4.4 × 10¹² cm^-2).

Conclusions:

• hBN-encapsulated graphene exhibits significantly higher electron saturation velocities than silicon and graphene on SiO₂.
• The enhanced performance is likely due to reduced scattering from surface optical phonons in hBN.
• These findings highlight the potential of hBN-encapsulated graphene for high-speed electronic applications.