Fast and Sensitive Terahertz Detection in a Current-Driven Epitaxial-Graphene Asymmetric Dual-Grating-Gate FET Structure

TL;DR

This paper presents a novel epitaxial-graphene FET with an asymmetric dual-grating-gate structure that achieves fast, sensitive terahertz detection at room temperature, demonstrating dual detection mechanisms and potential for high-speed wireless communications.

Contribution

The study introduces a new ADGG-structured EG-FET that combines plasmonic and photothermoelectric detection mechanisms, with experimentally demonstrated high responsivity and ultrafast response times.

Findings

Achieved 10-ps response time and 0.3 mA/W responsivity at 0.95 THz.

Identified coexistence of plasmonic and photothermoelectric detection mechanisms.

Photothermoelectric detection shows nearly twice the responsivity of plasmonic detection.

Abstract

We designed and fabricated an epitaxial-graphene-channel field-effect transistor (EG-FET) featured by the asymmetric dual-grating-gate (ADGG) structure working for a current-driven terahertz detector, and experimentally demonstrated a 10-ps order fast response time and a high responsivity of 0.3 mA/W to the 0.95-THz radiation incidence at room temperatures. The ADGG- and the drain-source-bias dependencies of the measured photoresponse showed a clear transition between plasmonic detection under periodic electron density modulation conditions with depleted regions and photothermoelectric detection under highly doped conditions without depleted regions. We identified the photothermoelectric detection that we observed as a new type of unipolar mechanism in which only electrons or holes contribute to rectifying the THz radiation under current-driven conditions. These two detection mechanisms coexist in a certain wide transcendent range of the applied bias voltages. It was also clearly manifested that the temporal photoresponse of the plasmonic and photothermoelectric detection are comparably fast on the order of 10 ps, whereas the maximal photoresponsivity of the photothermoelectric detection is almost twice as high as that of the plasmonic detection under the applied biases conditions. These results suggest that the ADGG-EG-FET THz detector will be promising for use in 6G- and 7G-class high-speed wireless communication systems.