High-Speed, High-Sensitivity Terahertz Detection

A research team has successfully devised a room-temperature terahertz-wave detector with both high speed and sensitivity, paving the way for advancements in the evolution of next-generation 6G/7G technology.

High-Speed, High-Sensitivity Terahertz Detection for 6G/7G Evolution
A bird's-eye view of the device structure and electron micrographs of the device surface. G1: gate 1 electrode, G2: gate 2 electrode, D: drain electrode, and S: source electrode. Image Credit: Akira Satou et al.

The details of this groundbreaking achievement were documented in the journal Nanophotonics on November 9th, 2023.

The improvement of current communication speeds is contingent upon terahertz (THz) waves, which constitute electromagnetic waves within the THz range, positioned between the microwave and infrared segments of the electromagnetic spectrum. These waves typically cover frequencies from 300 gigahertz to 3 THz.

However, conventional electronic- or photonic-based semiconductor devices face challenges in achieving fast and sensitive detection of THz waves at room temperature.

This is where two-dimensional plasmons play a crucial role. Within a semiconductor field-effect transistor, a two-dimensional electron channel exists, housing collective charge-density quanta, known as two-dimensional plasmons.

These plasmons represent excited states of electrons that display fluid-like behaviors. Their promise lies in the nonlinear rectification effects derived from these fluid-like behaviors, coupled with their rapid response, unhampered by electron transit time. Together, these attributes position two-dimensional plasmons as a compelling means for detecting THz waves at room temperature.

We discovered a 3D plasmonic rectification effect in THz wave detector. The detector was based on an indium-phosphide high-electron mobility transistor and it enabled us to enhance the detection sensitivity more than one order of magnitude higher than conventional detectors based on 2D plasmons.

Akira Satou, Associate Professor, Research Institute for Electrical Communication, Tohoku University

The innovative detection technique seamlessly integrated the conventional vertical hydrodynamic nonlinear rectification effect of 2D plasmons with the introduction of vertical diode-current nonlinearity.

This approach significantly addressed the waveform distortion arising from multiple reflections of high-speed modulated signals, a pivotal challenge in conventional detectors relying on 2D plasmons.

Heading the research team alongside Satou was Specially Appointed Professor Tetsuya Suemitsu from Tohoku University’s New Industry Creation Hatchery Center and Hiroaki Minamide from RIKEN Center for Advanced Photonics.

Our new detection mechanism overcomes most of the bottlenecks in conventional terahertz-wave detectors. Looking ahead, we hope to build on our achievement by improving the device performance.

Akira Satou, Associate Professor, Research Institute for Electrical Communication, Tohoku University

Journal Reference:

Satou, A., et al. (2023) Gate-readout and a 3D rectification effect for giant responsivity enhancement of asymmetric dual-grating-gate plasmonic terahertz detectors. Nanophotonics. doi.org/10.1515/nanoph-2023-0256.

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