Abrupt p-n junction using ionic gating at zero-bias in bilayer graphene

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Graphene's unique electronic properties make it suitable for optoelectronic devices.
• Fabricating controlled p-n junctions in graphene is crucial for advanced electronic applications.
• Previous methods often resulted in graded junctions, limiting device performance.

Purpose of the Study:

• To develop a novel method for creating abrupt p-n junctions in bilayer graphene FETs.
• To investigate the photovoltage characteristics of these junctions at low temperatures.
• To explore the underlying physical mechanisms responsible for the observed photovoltage.

Main Methods:

• Fabrication of a double gated bilayer graphene field-effect transistor (FET).
• Utilized a combination of electrostatic and electrolytic gating to form an abrupt p-n junction.
• Measured photovoltage at low temperatures with a frozen electrolyte.

Main Results:

• Confirmed the formation of an abrupt p-n junction via two Dirac peaks in the gating curve.
• Observed a six-fold pattern in photovoltage at low temperatures, indicating the photothermoelectric effect.
• Photovoltage increased with decreasing temperature, suggesting dominant supercollision scattering.

Conclusions:

• The developed dual-gating technique successfully creates abrupt graphene p-n junctions.
• The photothermoelectric effect and supercollision scattering play significant roles in the device's photoresponse.
• This technique is extendable to other 2D materials for large-area superlattice p-n junctions with enhanced photoresponse.