Compact Graphene Plasmonic Slot Photodetector on Silicon-on-Insulator with High Responsivity
Zhizhen Ma, Kazuya Kikunaga, Hao Wang, Shuai Sun, Rubab Amin, Rishi Maiti, Mohammad H. Tahersima, Hamed Dalir, Mario Miscuglio, Volker J. Sorger
Abstract
Graphene has extraordinary electro-optic properties and is therefore a promising candidate for monolithic photonic devices such as photodetectors. However, the integration of this atom-thin layer material with bulky photonic components usually results in a weak light–graphene interaction, leading to large device lengths, limiting electro-optic performance. In contrast, here we demonstrate a plasmonic slot graphene photodetector on silicon-on-insulator platform with high responsivity of 0.7 A/W given a just 5 μm short device length. We observe that the maximum photocurrent and, hence, the highest responsivity, scales inversely with the slot width. Using a dual-lithography step, we realize 15 nm narrow slots that show a 30× higher responsivity per unit device-length when compared to photonic graphene photodetectors. Furthermore, we reveal that the back-gated electrostatics is overshadowed by channel-doping contributions induced by the contacts of this ultrashort channel graphene photodetector. This leads to quasi charge neutrality, which explains both the previously unseen offset between the maximum photovoltaic-based photocurrent relative to graphene’s Dirac point and the observed nonambipolar transport characteristics. Such micrometer-compact and absorption-efficient photodetectors allow for short-carrier pathways in next-generation photonic components, while being offering a testbed for studying short-channel carrier physics in graphene optoelectronic devices.