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<p>We are reporting the fabrication of a graphene-based all-electrical THz modulator on Si/HfO<sub>2</sub> heterostructure which exhibits a high modulation depth of 28.7% at room temperature. The single-layer graphene as an active layer, highly resistive Si substrate, HfO<sub>2</sub> as a high-k dielectric layer, back ring contact on the back side of the substrate, and a ring-type metal mesh as top contact was used to fabricate the electrical THz modulator. Mesh-type top electrode contact was advantageous for uniform distribution of applied electric field over the whole graphene active area and HfO<sub>2</sub> is deposited to harness its high dielectric constant. THz transmission modulation was measured for 0.3–0.45 THz frequency range with applied electrical bias from −1.5 to 25&#xa0;V. Maximum modulation depth = 28.7% was achieved at 25&#xa0;V. We have theoretically simulated the variation of modulation depth with the applied bias of the device using Drude conductivity model. The comparison of the experimental result with the simulated result shows good agreement for dielectric constant 18 of HfO<sub>2</sub> and graphene mobility as 2000&#xa0;cm<sup>2</sup>/V-sec. Our study shows that graphene on Si/HfO<sub>2</sub> heterostructure exhibits great potential for developing an efficient, room temperature, and compact all-electrical THz modulator.</p>

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Si/HfO2/graphene heterostructure for efficient all-electrical THz modulator

  • 期刊论文

  • 发表日期：

    2025年8月3日

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  • Abhilasha Chouksey,
  • Mohan Lal,
  • Shivnath Kumar,
  • Prashant Kumar,
  • Radhapiyari Laishram,
  • Anupama Singh,
  • J. S. Rawat,
  • Neeraj Khare

摘要

We are reporting the fabrication of a graphene-based all-electrical THz modulator on Si/HfO2 heterostructure which exhibits a high modulation depth of 28.7% at room temperature. The single-layer graphene as an active layer, highly resistive Si substrate, HfO2 as a high-k dielectric layer, back ring contact on the back side of the substrate, and a ring-type metal mesh as top contact was used to fabricate the electrical THz modulator. Mesh-type top electrode contact was advantageous for uniform distribution of applied electric field over the whole graphene active area and HfO2 is deposited to harness its high dielectric constant. THz transmission modulation was measured for 0.3–0.45 THz frequency range with applied electrical bias from −1.5 to 25 V. Maximum modulation depth = 28.7% was achieved at 25 V. We have theoretically simulated the variation of modulation depth with the applied bias of the device using Drude conductivity model. The comparison of the experimental result with the simulated result shows good agreement for dielectric constant 18 of HfO2 and graphene mobility as 2000 cm2/V-sec. Our study shows that graphene on Si/HfO2 heterostructure exhibits great potential for developing an efficient, room temperature, and compact all-electrical THz modulator.