Abstract-High-speed and broadband terahertz wave modulators based on large-area graphene field-effect transistors

Qi Mao, Qi-Ye Wen, Wei Tian, Tian-Long Wen, Zhi Chen, Qing-Hui Yang, and Huai-Wu Zhang  »View Authors http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-19-5649 Optics Letters, Vol. 39, Issue 19, pp. 5649-5652 (2014) http://dx.doi.org/10.1364/OL.39.005649

We present a broadband terahertz wave modulator with improved modulation depth and switch speed by cautiously selecting the gate dielectric materials in a large-area graphene-based field-effect transistor (GFET). An ultrathin Al2O3film (∼60  nm) is deposited by an atomic-layer-deposition technique as a high-k gate dielectric layer, which reduces the Coulomb impurity scattering and cavity effect, and thus greatly improves the modulation performance. Our modulator has achieved a modulation depth of 22% and modulation speed of 170 kHz in a frequency range from 0.4 to 1.5 THz, which is a large improvement in comparison to its predecessor of SiO2-based GFET.

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