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Graphene Zero-Bias Sub-Terahertz Turnkey Detector with Above 43 GHz Bandwidth

E. I. Titova, A. Titchenko, M. Titova, K. Shein, A. Kuksov, A. Sobolev, M. Kashchenko, M. Kravtsov, L. Elesin, K. S. Novoselov, G. Goltsman, D. A. Svintsov, I. Gayduchenko, D. A. Bandurin

Abstract

High-frequency terahertz (THz) detectors are vital for next-generation high-speed wireless communication systems. Graphene, with its high carrier mobility, broadband absorption, and weak electron-phonon coupling, offers great promise for ultra-fast THz photothermoelectric devices. Although graphene-based detectors in the infrared range have shown bandwidths above 500 GHz, extending their operation to the THz range is difficult because long-wavelength radiation does not efficiently couple to the small graphene area. To overcome this issue, THz antennas are often employed; however, their use typically limits system performance to only a few gigahertz due to parasitic effects. In this work, we present an antenna-coupled sub-THz graphene detector with a bandwidth exceeding 43 GHz. We optimized the detector design to minimize losses, match the antenna impedance to the 1 kOhm graphene channel, and maintain zero-bias operation. Importantly, we introduce a compact, turnkey packaged solution. Our results provide a practical route toward high-speed and low-power graphene THz detectors suitable for real-world communication and imaging applications.

Graphene Zero-Bias Sub-Terahertz Turnkey Detector with Above 43 GHz Bandwidth

Abstract

High-frequency terahertz (THz) detectors are vital for next-generation high-speed wireless communication systems. Graphene, with its high carrier mobility, broadband absorption, and weak electron-phonon coupling, offers great promise for ultra-fast THz photothermoelectric devices. Although graphene-based detectors in the infrared range have shown bandwidths above 500 GHz, extending their operation to the THz range is difficult because long-wavelength radiation does not efficiently couple to the small graphene area. To overcome this issue, THz antennas are often employed; however, their use typically limits system performance to only a few gigahertz due to parasitic effects. In this work, we present an antenna-coupled sub-THz graphene detector with a bandwidth exceeding 43 GHz. We optimized the detector design to minimize losses, match the antenna impedance to the 1 kOhm graphene channel, and maintain zero-bias operation. Importantly, we introduce a compact, turnkey packaged solution. Our results provide a practical route toward high-speed and low-power graphene THz detectors suitable for real-world communication and imaging applications.
Paper Structure (4 sections, 2 figures)

This paper contains 4 sections, 2 figures.

Table of Contents

  1. Fast THz Graphene detector
  2. High-frequency THz measurements
  3. Results and Discussion
  4. Conclusions

Figures (2)

  • Figure 1: Zero-bias graphene-based ultrafast THz detector(a) Optical photograph of the graphene device consisting of a THz antenna, low‑pass choke filters, and a coplanar waveguide. The photovoltage is readout between source (S) and drain (D) electrodes. Scale bar: 500 $\mu$m. The inset shows a zoomed-in view of the double-slot THz antenna structure. Scale bar: 100 $\mu$m. The right inset shows the asymmetric tooth structure adjacent to the graphene channel, designed to generate a zero‑bias photoresponse. Scale bar: 1 $\mu$m. The upper right inset shows schematic of the high-frequency graphene photodetector implemented with a silicon sphere lens. (b) Simulated electric field distribution in the antenna-coupled graphene detector under 130 GHz illumination, showing field enhancement in the graphene active area. Scale bar: 500 $\mu$m. (c) Calculated impedance ($Z_{in}$) and S-parameter of the sub-THz antenna. (d) Measured I–V curves of the graphene channel with (red) and without (black) THz illumination.
  • Figure 2: Electrically measured response time and bandwidth (BW) of the THz graphene detector. (a) Heterodyne measurement scheme. Two THz sources are combined using a beamsplitter (BS) to illuminate the detector, with the signal recorded by an a electrical spectrum analyzer (ESA) at the intermediate frequency $\rm{IF} = |f_{\mathrm{source_1}} - f_{\mathrm{source_2}}|$. A Golay cell monitors THz power. (b) Photograph of the packaged detector module with integrated RF connector and Si hyper-hemispherical lens. (c) High-frequency PCB assembly with coplanar waveguide contacting the graphene device. (d) Measured detector signal‑to‑noise photoresponse as a function of the intermediate frequency. The flat dependence indicates a bandwidth well above 43 GHz (corresponding to a response time of $t = 1/(2\pi f) \approx 3.7 ps$), limited by the measurement setup.