2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators

Hitesh Agarwal; Bernat Terrés; Lorenzo Orsini; Alberto Montanaro; Vito Sorianello; Marianna Pantouvaki; Kenji Watanabe; Takashi Taniguchi; Dries Van Thourhout; Marco Romagnoli; Frank H. L. Koppens

doi:10.1038/s41467-021-20926-w

Article 2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators

Hitesh Agarwal ; Bernat Terrés ; Lorenzo Orsini ; Alberto Montanaro ; Vito Sorianello ; Marianna Pantouvaki ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Dries Van Thourhout ; Marco Romagnoli ; Frank H. L. Koppens

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Hitesh Agarwal, Bernat Terrés, Lorenzo Orsini, Alberto Montanaro, Vito Sorianello, Marianna Pantouvaki, Kenji Watanabe, Takashi Taniguchi, Dries Van Thourhout, Marco Romagnoli, Frank H. L. Koppens. 2D-3D integration of hexagonal boron nitride and a high-κ dielectric for ultrafast graphene-based electro-absorption modulators. Nature Communications. 2021, 12 (1), 1070. https://doi.org/10.1038/s41467-021-20926-w

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Electro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon (Si) devices, graphene- based EA modulators promise smaller footprints, larger temperature stability, cost-effective inte- gration and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. In this work, we overcome this fundamental trade-off by demonstrating the first 2D-3D dielectric integration in a high-quality encapsulated graphene device. We integrated hafnium oxide (HfO2 ) and two-dimensional (2D) hexagonal boron nitride (hBN) within the insulating section of a double-layer (DL) graphene EA modulator. This novel combination of materials allows for a high-quality modulator device with record high performance: bandwidth (BW) beyond 40GHz with a three-fold increase in modulation efficiency compared to previously reported high-speed modulators. This first demonstration of 2D-3D integration paves the way to a pletora of electronic and opto-electronic devices with enhanced performance and stability, while expanding the freedom for device design.

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