Highly sensitive broadband binary photoresponse in gateless epitaxial graphene on 4H-SiC

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Standard graphene photodetectors exhibit low photoresponsivity (mA/W) due to weak light-matter interactions.
• Epitaxial graphene (EG) on 4H-SiC offers enhanced photoresponse and utilizes an interfacial buffer layer (IBL) for electron carriers.

Purpose of the Study:

• To demonstrate a gate-free, planar EG/4H-SiC photodetector with broadband detection capabilities.
• To investigate the origin of the broadband binary photoresponse in EG/4H-SiC devices.

Main Methods:

• Fabrication of a planar epitaxial graphene on 4H-SiC device.
• Characterization of the device's photoresponse under various laser wavelengths (405-980 nm).
• Analysis of the energy band alignment and work function of the EG/IBL interface.

Main Results:

• The device exhibits a broadband binary photoresponse, with positive response for 405-532 nm and negative for 632-980 nm laser excitation.
• Achieved photoresponsivity > 10 A/W at 405 nm with a power density of 7.96 mW/cm² and 1 V bias.
• Photoresponsivity is three orders of magnitude higher than CVD/exfoliated graphene devices, meeting practical application requirements.

Conclusions:

• The broadband binary photoresponse is attributed to the IBL/EG interface band alignment and EG's work function.
• EG/4H-SiC devices offer a viable platform for high-performance broadband photodetection.
• This research opens avenues for selective light-triggered logic devices and advanced photodetectors.