Current saturation and voltage gain in bilayer graphene field effect transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electrical Engineering

Background:

• Graphene's unique electrical properties offer potential for high-frequency electronic devices.
• Graphene field-effect transistors (GFETs) have demonstrated high cutoff frequencies but suffer from poor voltage gain.
• Analog high-frequency applications require both high cutoff frequencies and substantial voltage gain.

Purpose of the Study:

• To enhance the voltage gain of graphene field-effect transistors (GFETs).
• To investigate the impact of bilayer graphene and electric displacement fields on GFET performance.
• To explore the feasibility of this approach for sub-100 nm gate length devices.

Main Methods:

• Utilizing bilayer graphene to introduce a tunable band gap via a vertical electric displacement field.
• Characterizing GFET performance, focusing on voltage gain and transconductance.
• Employing numerical simulations based on an atomistic p(z) tight-binding Hamiltonian.

Main Results:

• Bilayer GFETs achieved an intrinsic voltage gain of up to 35 at a displacement field of -1.7 V/nm.
• This represents a six-fold improvement in voltage gain compared to monolayer GFETs.
• Transconductance, crucial for cutoff frequency, remained unaffected by the displacement field in both monolayer and bilayer GFETs.

Conclusions:

• Introducing a band gap in bilayer graphene via an electric field significantly boosts voltage gain without compromising transconductance.
• This method offers a viable pathway for developing high-performance GFETs for analog high-frequency applications.
• The approach is demonstrated to be effective for sub-100 nm gate lengths through numerical simulations.