title: High-speed and broadband terahertz wave modulators based on large-area graphene field-effect transistors.
abstract: 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 Al2O3 film (∼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.
authors.forename: Qi
authors.initials: Q
authors.lastname: Mao
authors.forename: Qi-Ye
authors.initials: QY
authors.lastname: Wen
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.forename: Tian-Long
authors.initials: TL
authors.lastname: Wen
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Qing-Hui
authors.initials: QH
authors.lastname: Yang
authors.forename: Huai-Wu
authors.initials: HW
authors.lastname: Zhang