Researchers from ICFO, ETH Zurich, University of Ioannina, Catalan Institute of Nanoscience and Nanotechnology (ICN2), Arizona State University and Japan's National Institute for Materials Science have demonstrated the first graphene‑based sub‑terahertz (sub‑THz) direct receivers that simultaneously deliver multi‑gigabit‑per‑second data rates, ultra‑compact footprint, CMOS compatibility, and near‑zero operating power - making graphene a valid hardware candidate for 6G wireless communications.
They operate at sub‑THz carrier frequencies to meet the demanding requirements of future links, achieving multi‑gigabit‑per‑second wireless data transmission over distances of around 3 m at room temperature, with a fully electronic, zero‑bias detection scheme and a device area of only about 0.018 mm².
The receivers combine a high‑mobility graphene channel with a resonant on‑chip sub‑THz antenna, a high‑Q cavity, and a back mirror underneath a sub‑THz‑transparent silicon substrate to strongly enhance the interaction between incident radiation and the atomically thin graphene layer. The graphene channel is engineered with reduced resistance and impedance close to 50 Ω, enabling efficient power transfer to standard RF electronics. Detection relies on the photothermoelectric effect in graphene, which converts tiny sub‑THz–induced changes in electron temperature into a strong electrical signal at zero bias, providing both high sensitivity and negligible power consumption.
Experiments reveal a clear bandwidth-responsivity trade-off across devices: a low-responsivity configuration shows a setup‑limited 3 dB bandwidth of 40 GHz, while a more sensitive device exhibits a responsivity of 0.16 A/W (≈30 V/W) and a noise‑equivalent power of 58 pW/√Hz at an electrical bandwidth of about 2 GHz. Simulations indicate that this architecture can, in principle, reach more than 300 GHz of bandwidth, responsivities on the order of 1 A/W (around 120 V/W), and NEP values near 14 pW/√Hz, pointing to substantial headroom for further optimization. The direct detection scheme and on‑chip antenna remove the need for bulky horn antennas or optical front‑ends, and the carbon‑based, dry‑etched graphene process is naturally compatible with CMOS back‑end lines, facilitating dense on‑chip integration and array architectures.
This combination of performance and integration distinguishes these devices from previously reported graphene detectors in the sub‑THz range, which had not demonstrated data‑stream reception. Thanks to graphene’s intrinsically high bandwidth - supported by >400 GHz bandwidth observations at telecom wavelengths in related PTE detectors - sub‑THz graphene receivers are expected to ultimately support data rates beyond 500 Gbit/s.
Future efforts will focus on arrays of graphene receivers to collect more incident power and reduce the need for external amplification, as well as on scalable CVD graphene with mobilities in the ~20,000–30,000 cm²/Vs range and operation near the charge‑neutrality point, all of which are expected to further boost responsivity and bandwidth and solidify graphene’s role in next‑generation 6G hardware.
