Victor Ryzhii

We propose and analyze the characteristics of the terahertz tunneling plasmonic detectors (TPDs) based on ungated graphene metastructures consisting of the graphene microribbons (GMRs) and connected by arrays of the graphene-nanoribbons (GNRs). The operation of the graphene TPDs is associated with the tunneling nonlinearity of the lateral n-GMR/I-GNR/p-GMR junction. The excitation of double-edge plasmonic oscillations leads to the resonant amplification of the ac tunneling current and the rectified current. The implementation of the lateral n-GMR/I-GNR/p-GMR junctions results in a decrease of its capacitance. The advantages of TPDs can further enhance the performance of THz detectors.

We analyze the thermal and electrical characteristics of the metasurface composed of a coplanar interdigital array of the graphene microribbons (GMRs) connected by nanobridges (NBs). These nanobridges could be implemented using graphene nanoribbons (GNRs) or black-arsenic-phosphorus (b-AsP) nanostructures. When a bias voltage applied between neighboring GMRs, it induces electron and hole two-dimensional systems within the GMRs, leading to thermionic currents that flow through the connecting NB resulting in the self-heating effect. This self-heating effect increases the thermionic currents, creating an effective positive feedback loop between the carrier effective temperature and the injected currents, and the bias voltage. This mechanism may lead to thermal breakdown enabling threshold behavior of current–voltage characteristics and yielding an S-shaped response. The devices based on the GMR/GNR and GMR/AsP metasurface structures can serve as fast voltage-controlled current switches, sensors, thermal terahertz and infrared sources, and among other applications.

The terahertz (THz) frequency range (0.1–10 THz) bridges the electronic and photonic spectral domains and offers key opportunities for high-speed communication, sensing, and spectroscopy. However, the realization of compact, coherent, and room-temperature THz sources and detectors remains still a long-standing challenge. Recent advances in two-dimensional (2D) materials, hosting graphene-like massless Dirac fermions, have opened some new paths toward overcoming this limitation. This paper reviews recent advances in the physics of Dirac plasmons in graphene and related 2D heterostructure materials and their THz device applications. It first outlines the fundamentals of 2D plasmon hydrodynamics, nonlinearities, and current-driven instabilities, including Dyakonov–Shur Ryzhii–Satou–Shur, and Cherenkov-type mechanisms. A new mechanism, Coulomb drag instability, recently discovered by the authors, is theoretically shown to provide the largest plasmonic gain among these mechanisms, offering a new route to efficient THz amplification and lasing. Its experimental verification is currently in progress. The review also discusses graphene-based plasmonic lasers, amplifiers, and detectors, and recent developments in graphene/black-arsenic–phosphorus heterostructures that enable band-structure and plasmonic engineering. Finally, topological-insulator-based heterostructures are introduced as promising material systems. These advances demonstrate that Dirac plasmon physics provides a robust foundation for next-generation THz device technology.

We review recent progress in the development of graphene-based topological structures for terahertz (THz) plasmonic applications. Our focus is on perforated graphene layers (PGLs), composed of coplanar graphene microribbon (GMR) arrays interconnected by graphene nanoribbon (GNR) bridges. These structures exhibit resonant plasmonic behavior and nonlinear inter-ribbon transport, enabling efficient THz detection through rectification and bolometric mechanisms. The plasmonic frequency is tunable via bias-induced carrier injection. Depending on the structural and transport parameters, the PGL devices can exhibit S-type current–voltage characteristics due to strong carrier heating and double injection feedback. Numerical analysis of the responsivity and spectral characteristics demonstrates strong resonance effects and indicates the feasibility of compact, high-performance THz sensors and photomixers based on these structures.

We investigate the carrier transport characteristics of a perforated graphene layer (PGL) composed of arrays of interdigital coplanar graphene microribbons (GMRs) connected by graphene nanoribbon (GNR) bridges. Our analysis focuses on their operation at room temperature. Under an applied bias voltage, two-dimensional electron and hole systems (2DES and 2DHS) form in adjacent GMRs. The terminal current in these PGL structures is primarily governed by thermionic transport across the GNR bridges. As electrons and holes traverse the GNRs, they induce heating in the 2DES and 2DHS, creating a positive feedback loop between carrier heating and thermionic emission. This phenomenon, known as hot-carrier thermal breakdown, can give rise to S-shaped inter-GMR current–voltage characteristics. These unique transport properties make PGLs promising candidates for fast, voltage-controlled room-temperature switches and electromagnetic radiation detectors.

We propose and evaluate the characteristics of the terahertz (THz) detectors based on perforated graphene layers (PGLs). The PGL structures constitute the interdigital in-plane arrays of the graphene microribbons (GMRs) connected by the sets of narrow constrictions, which form the graphene nanoribbon bridges (GNRs). The PGL detector operation is associated with the rectification and hot-carrier bolometric mechanisms. The excitation of plasmonic oscillations in the GMR-GNR arrays can reinforce these mechanisms. The room-temperature PGL detector responsivity and detectivity are calculated as a function of radiation frequency and device structure parameters. The effects of the rectification and hot-carrier mechanisms are compared. The PGL THz detectors under consideration can exhibit highly competitive values of responsivity and detectivity.

The lateral interdigital array of the graphene microribbons (GMRs) on the h-BN substrate connected by narrow graphene nanoribbon (GNR) bridges serves as an efficient detector of terahertz (THz) radiation. The detection is enabled by the nonlinear GNR elements providing the rectification of the THz signals. The excitation of plasmonic waves along the GMRs (transverse plasmonic oscillations) by impinging THz radiation can lead to a strong resonant amplification of the rectified signal current and substantial enhancement of the detector response. The GMR arrays with the GNR bridges can be formed by the perforation of uniform graphene layers.

We analyze the operation of the hot-electron FET bolometers with the graphene channels (GCs) and the gate barrier layers. Such bolometers use the thermionic emission of the hot electrons heated by incident-modulated THz radiation. The hot electrons transfer from the GC into the metal gate. As the THz detectors, these bolometers can operate at room temperature. We show that the response and ultimate modulation frequency of the GC-FET bolometers are determined by the efficiency of the hot-electron energy transfer to the lattice and the GC side contacts due to the 2DEG lateral thermal conductance. The dependences of these mechanisms on the band structure and geometrical parameters open the way for the GC-FET bolometers optimization, in particular, for the enhancement of the maximum modulation frequency.

In this paper, we analyze the modulation characteristics and the ultimate modulation frequency of the terahertz (THz) hot-electron FET bolometers with the graphene channels (GCs), metal gate (MG), and gate barrier layers (BLs) in a wide temperature range. Our results predict that the responsivity of GC-FET bolometers decreases with decreasing operating temperature. This is attributed to a dramatic drop in the thermionic GC-MG current (characterized by the relatively large activation energy) and its modulated component when the temperature lowers. A further decrease in the temperature results in a fairly strong responsivity roll-off. In contrast, the responsivity of the GC-FET detectors with the temperature-adjusted load resistance rises with decreasing temperature because the temperature lowering leads to an increase in the electron energy relaxation time and promotes more effective heating by the impinging THz radiation. In this case, the weakening of the thermionic current is compensated by the commensurate increase in the load resistance.