Flexible Graphene Field-Effect Transistors Encapsulated in Hexagonal Boron Nitride

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Flexible electronics require high-performance transistors.
• Graphene field-effect transistors (GFETs) offer potential but face challenges in achieving optimal performance and stability.
• Hexagonal boron nitride (hBN) is explored as a dielectric material for graphene devices.

Purpose of the Study:

• To fabricate flexible GFETs with full hBN encapsulation using a self-aligned scheme.
• To evaluate the electronic and mechanical properties of these flexible GFETs.
• To demonstrate the potential of hBN as a robust dielectric for high-performance flexible graphene electronics.

Main Methods:

• Fabrication of flexible GFETs with graphene channels fully encapsulated in hBN.
• Implementation of a self-aligned fabrication scheme.
• Characterization of device performance, including carrier mobility, current saturation, and radio frequency (RF) characteristics.
• Assessment of mechanical flexibility under strain.

Main Results:

• Flexible GFETs (2 μm channel length) exhibited high room-temperature carrier mobility (μFE = 10,200 cm²/V·s) and strong current saturation (r0 = 2000 Ω).
• Flexible RF-FETs (375 nm channel length) achieved μFE = 2200 cm²/V·s and r0 = 132.5 Ω, with unity current gain (fT) and unity power gain (fmax) frequencies reaching 12.0 and 10.6 GHz, respectively.
• Record high fmax/fT ratio (0.9) and intrinsic fT/fmax of 29.7/15.7 GHz were observed.
• Devices demonstrated high mechanical flexibility with strain limits of 1%.

Conclusions:

• The full hBN encapsulation and self-aligned structure significantly improve the dielectric environment and electronic characteristics of flexible GFETs.
• hBN proves to be a mechanically robust dielectric material suitable for high-performance flexible graphene electronics.
• These findings pave the way for advanced graphene-based flexible electronic applications.