Ultrafast intrinsic optical-to-electrical conversion dynamics in a graphene photodetector

Optical-to-electrical conversion in graphene is a central phenomenon for realizing anticipated ultrafast and low-power-consumption information technologies. However, revealing its mechanism and intrinsic timescale require uncharted terahertz electronics and device architectures. Here we succeeded in...

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Published inNature photonics Vol. 16; no. 10; pp. 718 - 723
Main Authors Yoshioka, Katsumasa, Wakamura, Taro, Hashisaka, Masayuki, Watanabe, Kenji, Taniguchi, Takashi, Kumada, Norio
Format Journal Article
LanguageEnglish
Published London Nature Publishing Group UK 25.08.2022
Nature Publishing Group
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Summary:Optical-to-electrical conversion in graphene is a central phenomenon for realizing anticipated ultrafast and low-power-consumption information technologies. However, revealing its mechanism and intrinsic timescale require uncharted terahertz electronics and device architectures. Here we succeeded in resolving optical-to-electrical conversion processes in high-quality graphene via the on-chip electrical readout of an ultrafast photothermoelectric current. By suppressing the time constant of a resistor–capacitor circuit using a resistive zinc oxide top gate, we constructed a gate-tunable graphene photodetector with a bandwidth of up to 220 GHz. Measuring the non-local photocurrent dynamics, we found that the photocurrent extraction from the electrode is quasi-instantaneous without a measurable carrier transit time across several-micrometre-long graphene, following the Shockley–Ramo theorem. The time for photocurrent generation is exceptionally tunable from immediate to >4 ps, and its origin is identified as Fermi-level-dependent intraband carrier–carrier scattering. Our results bridge the gap between ultrafast optical science and device engineering, accelerating ultrafast graphene optoelectronic applications. Researchers demonstrated a gate-tunable graphene photodetector with a bandwidth of up to 220 GHz. This was achieved by suppressing the ‘RC’ time constant using a resistive zinc oxide top gate.
ISSN:1749-4885
1749-4893
DOI:10.1038/s41566-022-01058-z