Competing channels for hot-electron cooling in graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene's unique electronic properties make it a promising material for optoelectronic devices.
• Understanding hot-electron dynamics is crucial for optimizing device performance.
• Photocurrent measurements provide insights into carrier behavior and energy relaxation processes.

Purpose of the Study:

• To investigate temperature-dependent photocurrent in dual-gated monolayer graphene p-n junctions.
• To probe hot-electron cooling channels and their temperature dependence.
• To demonstrate gate control over graphene's photoresponse.

Main Methods:

• Temperature-dependent photocurrent measurements from 4 K to 300 K.
• Utilizing dual-gated monolayer graphene p-n junction devices.
• Analyzing the photothermoelectric effect to determine hot-electron temperature and cooling dynamics.

Main Results:

• A nonmonotonic temperature dependence of peak photocurrent and hot spot size was observed.
• Two competing hot-electron cooling pathways were identified: normal collisions (low T) and supercollisions (high T).
• Gate control enabled the resolution of these two distinct cooling processes within the same device.

Conclusions:

• The study elucidates the interplay of different hot-electron cooling mechanisms in graphene.
• Gate-tunable photoresponse offers a novel method for controlling graphene-based devices.
• Findings provide a deeper understanding of energy dissipation in graphene.