Optoelectronic mixing with high-frequency graphene transistors.

Area of Science:

• Optoelectronics
• Materials Science
• Electrical Engineering

Background:

• Graphene exhibits ideal properties for optoelectronics, including absorption at telecom wavelengths, high-frequency operation, and CMOS-compatibility.
• Existing optoelectronic devices face limitations in achieving high-speed signal mixing for advanced applications.

Purpose of the Study:

• To demonstrate high-speed optoelectronic mixing using graphene field-effect transistors (GFETs).
• To investigate the influence of the single-layer graphene (SLG) Fermi level on photodetection mechanisms and photocurrent.
• To explore the potential of GFETs for millimeter-wave (mm-wave) applications.

Main Methods:

• Fabrication and characterization of GFETs capable of high-frequency operation (~20 GHz bandwidth).
• Mixing of an electrical gate signal with a modulated optical signal on the SLG channel.
• Analysis of photocurrent generation and sign dependency on the SLG Fermi level (E_F).

Main Results:

• GFETs successfully achieved high-speed optoelectronic mixing.
• Photocurrent sign reversal observed based on SLG Fermi level: positive at low E_F (<130 meV) and negative photobolometric current at high E_F (>130 meV).
• Devices demonstrated operational capability up to at least 67 GHz.

Conclusions:

• GFETs are effective for high-speed optoelectronic mixing, offering tunable photodetection mechanisms.
• The demonstrated performance paves the way for GFETs in mm-wave applications.
• Potential applications include advanced telecommunications and radio/light detection and ranging (RADAR/LIDARs).