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Proceedings Paper

Graphene p-n junction photo-responsivity enhanced with gap-plasmons (Conference Presentation)
Author(s): Di Wang; Andres E. Llacsahuanga Allcca; Ting-Fung Chung; Alexander V. Kildishev; Yong P. Chen; Alexandra Boltasseva; Vladimir M. Shalaev

Paper Abstract

Graphene photodetectors’ intrinsically low responsivity (sensitivity) has been a long-standing issue that overshadows graphene’s other excellent optical properties as a photodetection material. The key to improving the graphene photodetector responsivity lies in enhancing the photothermoelectric (PTE) effect, which has already been demonstrated to be the dominant photocarrier generation mechanism. To maximize the PTE current, one would need a strong optically-induced temperature gradient to overlap with a graphene p-n junction spatially. Here, the temperature gradient drives the charge carrier movement, while the graphene p-n junction separates the different charge carrier types (electrons and holes) and makes them drift in opposite directions. In this work, we show that these two conditions can be met simultaneously in a meticulously designed device, combining a gap plasmon structure and a pair of split-gates. The gap plasmon structure absorbs 71% of incident light creating localized heating (thereby large temperature gradient), and the split-gates create a p-n junction at the center of the localized thermal gradient. We fabricated a graphene photodetector with the proposed configuration, and experimentally verified the dominance of PTE effect in photocurrent generation in good agreement with theoretical calculations. More importantly, we obtained a responsivity 70 times higher than the previously reported value from a similar device without plasmon-enhancement. Moreover, originating from the combination of gap plasmon-enhanced optical absorption and optimized p-n junction, our responsivity is 5~7 times higher than reported values for other graphene photodetectors with different types of plasmon-enhancement and no junction control.

Paper Details

Date Published: 9 September 2019
Proc. SPIE 11080, Metamaterials, Metadevices, and Metasystems 2019, 1108011 (9 September 2019); doi: 10.1117/12.2539574
Show Author Affiliations
Di Wang, Purdue Univ. (United States)
Andres E. Llacsahuanga Allcca, Purdue Univ. (United States)
Ting-Fung Chung, Univ. of California, Berkeley (United States)
Purdue Univ. (United States)
Alexander V. Kildishev, Purdue Univ. (United States)
Yong P. Chen, Purdue Univ. (United States)
Alexandra Boltasseva, Purdue Univ. (United States)
Vladimir M. Shalaev, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 11080:
Metamaterials, Metadevices, and Metasystems 2019
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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