Peak-to-valley Current Ratio Research Articles

Two-Dimensional SnSe2(1-x)S2x/MoTe2 Antiambipolar Transistors with Composition Modulation for Multivalued Inverters.

Two-dimensional (2D) van der Waals heterostructures that embody the electronic characteristics of each constituent material have found extensive applications. Alloy engineering further enables the modulation of the electronic properties in these structures. Consequently, we envisage the construction and modulation of composition-dependent antiambipolar transistors (AATs) using van der Waals heterostructures and alloy engineering to advance multivalued inverters. In this work, we calculate the electron structures of SnSe2(1-x)S2x alloys and determine the energy band alignment between SnSe2(1-x)S2x and 2H-MoTe2. We present a series of vertical AATs based on the SnSe2(1-x)S2x/MoTe2 type-III van der Waals heterostructure. These transistors exhibit composition-dependent antiambipolar characteristics through the van der Waals heterostructure, except for the SnSe2/MoTe2 transistor. The peak current (Ipeak) decreases from 43 nA (x = 0.25) to 0.8 nA (x = 1) at Vds = -2 V, while the peak-to-valley current ratio (PVR) increases from 4.5 (x = 0.25) to 6.7 × 103 (x = 1) with a work window ranging from 30 to 47 V. Ultimately, we successfully apply several specific SnSe2(1-x)S2x/MoTe2 devices in binary and ternary logic inverters. Our results underscore the efficacy of alloy engineering in modulating the characteristics of AATs, offering a promising strategy for the development of multivalued logic devices.

Tunable Band‐to‐Band Tunneling and Conducting Path Transition in Local‐Control‐Gate Heterostructure Transistor

AbstractTransition metal dichalcogenide (TMD) material‐based heterostructures have exhibited great potential for building advanced architectures in novel logic devices. A local‐control‐gate (LCG) transistor based on MoTe2/MoS2 heterostructure is fabricated and analyzed, illustrating its tunable electrical characteristics and achieving band‐to‐band tunneling (BTBT) enhancement with an improved peak‐to‐valley current ratio (PVCR) value of 3.04. Compared to the basic dual‐gate tunnel field‐effect transistor (TFET) structure, adding LCG at the bottom not only isolates defect‐induced doping effects from the deposition of top gate dielectrics, but also paves the way for broader applications in multivalued logic and artificial intelligence. Aiming to further verify the operating mechanism of conducting path transition and electrical characteristic trends, commercial technology computer‐aided design (TCAD) is systematically employed assisted by density functional theory (DFT). So that the transition of conducting paths in the heterostructure channel including interlayer quantum effects can be visibly demonstrated while applying various voltages to the LCG. In summary, this work highlights the feasibility of a new LCG structure with tunable electrical characteristics and presents DFT‐assisted TCAD simulations for effective verifications.

Charge transfer mechanism for realization of double negative differential transconductance

With development of information age, multi-valued logic (MVL) technology utilizing negative differential transconductance (NDT) phenomenon has drawn attention as next-generation computing technology that can replace binary logic. However, because conventional NDT devices primarily use ternary logic, multiple-peak NDT device is required for higher-radix MVL that can process more datasets. Here, van der Waals double-peak anti-ambipolar transistor (AAT) as NDT device was developed by utilizing peak voltage (Vpeak) modulation of NDT peak. For realization of quaternary logic, Vpeak modulation technology was developed through charge transfer mechanism from channel, thereby shifting NDT peak and increasing peak-to-valley current ratio (PVCR). Furthermore, Double-peak AAT was implemented through parallel configuration of two AATs with different Vpeak values. Finally, quaternary inverter with four widely stable logic states was implemented by utilizing the developed double-peak AAT with two distinct NDT peaks and high PVCR. This double-peak AAT is expected to contribute to the development of next-generation MVL technology capable of processing datasets.

Record peak current density of over 1500 kA/cm2 in highly scaled AlN/GaN double-barrier resonant tunneling diodes on free-standing GaN substrates

This work demonstrates high-performance AlN/GaN double-barrier resonant tunneling diodes (RTDs) with high peak current density grown by plasma-assisted molecular beam epitaxy on c-plane free-standing GaN substrates, featuring stable and repeatable negative differential resistance (NDR) characteristics at room temperature. By scaling down the barrier thickness of AlN barrier and the lateral mesa size of collector, the record peak current density of 1551 kA/cm2 is achieved along with a peak-to-valley current ratio (PVCR) of 1.24, which is attributed to the reduced resonant tunneling time under thinner AlN barrier and the suppressed external incoherent valley current by reducing the dislocation number contained in the RTD device with the smaller size of collector. By statistically analyzing the NDR performance of RTD devices with different thicknesses of AlN barrier, the average peak current density increases from 145.7 to 1215.1 kA/cm2, while the average PVCR decreases from 1.45 to 1.1, correspondingly, accompanying with a decreased peak voltage from 6.89 to 5.49 V, with downscaling the AlN barrier thickness from 1.5 to 1.25 nm. The peak current density obtained in this work is the highest value among all the reported nitride-based RTDs up until now while maintaining high PVCR value simultaneously, which illustrates that ultra-scaled RTD based on vertical quantum-well structure and lateral collector size is a valuable approach for the development of nitride-based RTDs with excellent NDR characteristics and reveals their great potential applications in high-frequency oscillation sources and high-speed switch circuits.

Effect of Structural Parameters on Current-Voltage Properties of GaAs-based Resonant Tunneling Diodes Using Device Simulator

The resonant tunneling diode (RTD) was first introduced by Tsu and Esaki back in 1973. The RTD has a nano-meter scale dimension and is capable to operate in the terahertz range of frequency, thanks to its unique negative differential resistive (NDR) property. There are tons of potential of RTD capable to implement in many applications if the optimum scales and parameters of the RTD’s structure can be determined. Hence, this is the reason and purpose of this work being conducted. The effects of structural parameters of RTD are studied and analyzed. From the simulation results generated by the WinGreen simulator, the barrier layer thickness has exhibited to be the most performance-affective structural parameter for RTD, when compared to other parameters such as thicknesses of spacer and quantum-well layers, and doping concentration of emitter and collector layers. The highest peak-to-valley current ratio (PVCR) of InGaAs/AlAs RTD achieved is approximately 78.36 with its barrier layer thickness of 1.6 nm. For GaAs/AlAs RTD, the highest PVCR obtained is approximately 59.29 at 1.6 nm thick of its barrier layer.

Edge tailored MgO nanoribbon for negative differential resistance/nanointerconnect applications

The electronic and transport characteristics of selective edge hydrogenated MgO nanoribbons (MgONRs) are investigated using non-equilibrium Green’s function (NEGF) in combination with density functional theory (DFT). The selective edge hydrogenation influences the stability of nanoribbons with bare MgONR (BMgOB) being the most stable structure while the bare O-edge MgONR (HMgOB) is the least stable structure. Irrespective of edge passivation, all the structures are metallic in nature. The transport calculations reveal that the bare Mg-edge (BMgOH) nanoribbon exhibits ohmic current behavior while the other nanoribbons exhibit negative differential resistance (NDR) behavior. The HMgOB device exhibits a significant NDR behavior with a significantly high peak-to-valley current ratio (PVCR) of about 3.07 × 106. Further, the BMgOH device is explored extensively for nanointerconnect performance. The transmission eigenstates illustrate the bare Mg-edge atoms contribute to the flow of carriers in BMgOH device. The parasitic components of the BMgOH device such as quantum capacitance (CQ), kinetic inductance (LK), and quantum resistance (RQ) are measured to be 3.59 fF/μm, 37.50 nH/μm, 6.46 kΩ, respectively. In addition, the BMgOH interconnects are stable and have excellent delay (τ), power delay product (PDP), and frequency response over copper interconnects. In addition to line resistance and capacitance, crosstalk is proven to degrade the interconnect performance. The obtained findings suggest that the MgONRs can be potentially used to design nanointerconnects and NDR based nanoelectronic device design by tailoring the edge hydrogenation.

C-doped zigzag blue phosphorene nanoribbons for GMR, rectification behaviour and NDR based devices

ABSTRACT Based on density functional theory (DFT) and nonequilibrium Green's function (NEGF) framework, to study the monolayer (ML) blue phosphorene (BlueP) doped with C along zigzag direction, such as the structural stability, and electronic and transport properties. Interestingly, we found that doping engineering strategies can effectively transform monolayer ML ZBlueP doped with C into a spintronic nanodevice with a few unique transport properties. Firstly, our model showed a magnificently giant magnetoresistance (GMR) up to 10 4 under low bias. Secondly, a rectifier with a large rectification ratio (RR) of 10 5 was observed. Lastly, negative differential resistance with a peak-to-valley current ratio (PVCR) of 10 4 was observed. Our research shows a promising route towards the development of high-performance ML ZBlueP spintronics technology by doping with C atom. Our results indicate that our models have immense potential for application in nanoscale spintronic devices.

Investigation of Peak-to-Valley Current Ratio of GaN/AlN Resonant Tunneling Diodes

Peak-to-valley current ratios (PVCRs) achie-ved in GaN/AlN resonant tunneling diodes (RTDs) are less than 2, significantly less than their counterparts, such as InGaAs/AlAs RTDs (e.g., PVCR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 12). This has hindered their high-speed applications because the maximum self-oscillation frequency and minimum switching time generally increase and decrease with PVCR. In this article, we investigate the problem of low PVCR in GaN/AlN RTDs with both modeling and experiments. Firstly, we developed a Schrödinger equation-based solver for RTD simulations. While the solver gives reasonable agreement with the experimental current–voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> ) characteristics, such as the positions of resonant peaks, it predicts a much higher PVCR. Then, we conducted temperature dependence studies on GaN/AlN RTDs and compared them with InGaAs/AlAs RTDs. The similarities observed suggest that sequential tunneling with phase randomization, resulting from scattering processes such as optical phonon and interface roughness scattering, is responsible for the large valley currents in GaN/AlN RTDs.

Highly Tunable Negative Differential Resistance Device Based on Insulator-to-Metal Phase Transition of Vanadium Dioxide.

Negative differential resistance (NDR) based on the band-to-band tunneling (BTBT) mechanism has recently shown great potential in improving the performance of various electronic devices. However, the applicability of conventional BTBT-based NDR devices is restricted by their insufficient performance due to the limitations of the NDR mechanism. In this study, we develop an insulator-to-metal phase transition (IMT)-based NDR device that exploits the abrupt resistive switching of vanadium dioxide (VO2) to achieve a high peak-to-valley current ratio (PVCR) and peak current density (Jpeak) as well as controllable peak and valley voltages (Vpeak/valley). When a phase transition is induced in VO2, the effective voltage bias on the two-dimensional channel is decreased by the reduction in the VO2 resistance. Accordingly, the effective voltage adjustment induced by the IMT results in an abrupt NDR. This NDR mechanism based on the abrupt IMT results in a maximum PVCR of 71.1 through its gate voltage and VO2 threshold voltage tunability characteristics. Moreover, Vpeak/valley is easily modulated by controlling the length of VO2. In addition, a maximum Jpeak of 1.6 × 106 A/m2 is achieved through light-tunable characteristics. The proposed IMT-based NDR device is expected to contribute to the development of various NDR devices for next-generation electronics.

Tuning the transport properties of tetracene-based single-molecule junctions with chemical or structural variation of side and anchoring groups.

This study aims to tune the transport properties of tetracene single-molecule junctions with the proper choice and placement of side and anchoring groups. For the operationalization of the molecule that was anchored with thiol or isocyanide groups, two different side groups, amine and nitro, in two different positions, were taken into consideration. For unperturbed tetracene molecule, a prominent negative differential resistance (NDR) feature at 1.8 V was observed with the isocyanide anchoring group while the thiol anchoring group exhibits a plateau region over a bias voltage of 2.2 to 3.2 V. At a bias voltage that is dependent on the chemical or structural change of side or anchoring groups, NDR feature of varying degree was seen in all configurations. Results show that the current flowing through the thiol-anchored molecule perturbed with the amine group at S' position is relatively larger than other configurations because of the smaller HOMO-LUMO gap and broader transmission peaks resulting in a peak to valley current ratio (PVCR) of 1.22. In addition, multiple NDR regions were realized in nitro-perturbed isocyanide-anchored molecule at S position. These results suggest their promising applications in switches, logic cells, and storage devices. The modeling and simulation of side-group mediated anchored tetracene molecule through two electrodic systems were studied using density functional theory (DFT) combined with non-equilibrium Green's function (NEGF) in Virtual NanoLab-AtomistixToolkit (ATK). The electron transport properties were calculated using Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation function. To optimize computing time, gold electrodes were single zeta polarized whereas the molecule, anchor groups, and side groups were double zeta polarized.

2-D tunneling structures and increased peak to valley current ratio in double barrier quantum systems under perpendicular electric and magnetic bias

Tunneling across an electrically biased double barrier system (with potential V along the z-axis) in a transverse magnetic field B (along the x-axis) is studied. The magnetic field-induced coupling of the transverse momentum (ky) with the z-direction motion of the electron selects the minimum value of ky depending on the incident energy εz below which the wave becomes evanescent in nature and is restricted from participating in the tunneling process. With the increase in B, resonant tunneling across the DBS occurs for an increasing range of resonant energy εzr albeit at a particular transverse momentum kyr for each εzr. Thus, the one-dimensional resonant tunneling feature at the quasi-resonant energy εzr0 for the entire spectrum of ky in absence of the magnetic field changes to a two-dimensional resonance structure in the εy and εz plane with the application of the magnetic field. The lower and upper bound of εzr and the corresponding limits on kyr for resonant tunneling based on B and V is spelt out. A formula for current density based on these observations is developed and the current–voltage relation for the DBS in presence of the transverse magnetic field is studied. With the application of the magnetic field the Peak to Valley current ratio (PVCR) calculated on the basis of tunneling current increases by many folds. The effect of Zeeman splitting due to interaction of spin moment of conduction electrons with magnetic field on the tunnel current is discussed.

Hydrogenated cove-edge aluminum nitride nanoribbons for ultrascaled resonant tunneling diode applications: a computational DFT study

While synthesizing quasi-one-dimensional nanoribbons, there is a finite probability that edges have cove-edge defects. This paper focuses on the structural, electronic, and transport properties of cove-edge aluminum nitride nanoribbons (AlNNR) using density functional theory and the non-equilibrium Green’s function (NEGF) method. The cove-edge AlNNRs are thermodynamically stable and exhibit metallic behavior. Interestingly, the calculated current–voltage characteristics of the cove-edge AlNNR-based nanodevices show negative differential resistance (NDR). The H-AlN-Cove nanodevice exhibits high peak-to-valley current ratio (PVCR) of the order of 107. The calculated PVCR of the H-AlN-Cove nanodevice is 106 times higher than that of the silicene nanoribbon (SiNR) and graphene nanoribbon (GNR), and 104 times higher than that of the phosphorene nanoribbon (PNR) and arsenene nanoribbons (ANR)-based devices respectively. The NDR feature with high PVCR provides a prospect for the cove-edge AlNNR in nanodevice applications.

DFT investigation of hydrogenated cove-edged boron nitride nanoribbons for resonant tunneling diodes application

The cove-defect is found to improve the stability of the nanoribbons through bond length reconstructions at the cove-edge. Density functional theory (DFT) and non-equilibrium Green’s function (NEGF)-based first principles calculations are used to examine the structural, electronic, and quantum transport aspects of the hydrogenated cove-edge defective zigzag boron nitride nanoribbons (ZBNNRs). The additional electronic states, originated by dangling bonds at the cove-edges, exist across the Fermi level making these structures purely metallic. Additionally, with high peak-to-valley current ratios (PVCR), the quantum transport properties’ negative differential resistance (NDR) features are obtained. The highest PVCR is calculated to be 3.60 × 1016. The presented cove-edge defects can have a lot of potential for ultra-scaled devices including resonant tunnel diodes (RTDs), memory, and nanoswitches, according to the NDR phenomenon discovered in cove-edge ZBNNRs.

Theoretical Prediction of Semiconductor-Free Negative Differential Resistance Tunnel Diodes with High Peak-to-Valley Current Ratios Based on Two-Dimensional Cold Metals

The negative differential resistance (NDR) tunnel diodes are promising alternative devices for beyond-CMOS (complementary metal oxide semiconductor) computing because they offer several potential applications when integrated with transistors. We propose a semiconductor-free NDR tunnel diode concept that exhibits an ultrahigh peak-to-valley current ratio (PVCR) value. Our proposed NDR diode consists of two cold metal electrodes separated by a thin insulating tunnel barrier. The NDR effect stems from the unique electronic band structure of the cold metal electrodes; i.e., the width of the isolated metallic bands around the Fermi level as well as the energy gaps separating higher- and lower-lying bands determine the current–voltage (I–V) characteristics and the PVCR value of the tunnel diode. By proper choice of the cold metal electrode materials, either a conventional N-type or Λ-type NDR effect can be obtained. Two-dimensional (2D) nanomaterials offer a unique platform for the realization of proposed NDR tunnel diodes. To demonstrate the proof of concept, we employ the nonequilibrium Green function method combined with density functional theory to calculate the I–V characteristic of the lateral (AlI2/MgI2/AlI2) and vertical (NbS2/h-BN/NbS2) heterojunction tunnel diodes based on 2D cold metals. For the lateral tunnel diode, we obtain a Λ-type NDR effect with an ultrahigh PVCR value of 1016 at room temperature, while the vertical tunnel diode exhibits a conventional N-type NDR effect with a smaller PVCR value of about 104. The proposed concept provides a semiconductor-free solution for NDR devices to achieve the desired I–V characteristics with ultrahigh PVCR values for memory and logic applications.

Nitrogen-doped zinc oxide nanoribbons for potential resonant tunneling diode applications.

Armchair ZnONRs doped with nitrogen are investigated in the current manuscript for possible applications based on negative differential resistance (NDR). To conduct the theoretical research, we use density functional theory (DFT) in conjunction with the non-equilibrium Green's function (NEGF) formalism to carry out first principles computations. Pristine ZnONR (P-ZnONRs) is a semiconductor with a wide energy bandgap (Eg) of 2.53 eV. However, one edge N-doped ZnONRs (SN-ZnO) and both edge N-doped ZnONRs (DN-ZnO) are metallic. Partial density of states (PDOS) reveals that the metallicity is caused by the doped nitrogen atom. The transport characteristics analysis revealed the negative differential resistance (NDR) characteristics in the N-doped ZnONRs. The peak-to-valley current ratios (PVCR) are computed and measured to be 4.58 × 1021 and 1.83 × 1022 for SN-ZnO and DN-ZnO, respectively. The obtained findings suggest the significant potential of armchair ZnONRs for NDR-based applications such as switches, rectifiers, oscillators, memory devices, etc.

Low-Power Negative-Differential-Resistance Device for Sensing the Selective Protein via Supporter Molecule Engineering.

Van der Waals (vdW) heterostructures composed of atomically thin two-dimensional (2D) materials have more potential than conventional metal-oxide semiconductors because of their tunable bandgaps, and sensitivities. The remarkable features of these amazing vdW heterostructures are leading to multi-functional logic devices, atomically thin photodetectors, and negative differential resistance (NDR) Esaki diodes. Here, an atomically thin vdW stacking composed of p-type black arsenic (b-As) and n-type tin disulfide (n-SnS2 ) to build a type-III (broken gap) heterojunction is introduced, leading to a negative differential resistance device. Charge transport through the NDR device is investigated under electrostatic gating to achieve a high peak-to-valley current ratio (PVCR), which improved from 2.8 to 4.6 when the temperature is lowered from 300 to 100K. At various applied-biasing voltages, all conceivable tunneling mechanisms that regulate charge transport are elucidated. Furthermore, the real-time response of the NDR device is investigated at various streptavidin concentrations down to 1pm, operating at a low biasing voltage. Such applications of NDR devices may lead to the development of cutting-edge electrical devices operating at low power that may be employed as biosensors to detect a variety of target DNA (e.g., ct-DNA) and protein (e.g., the spike protein associated with COVID-19).

Cross-Coupled Gated Tunneling Diodes With Unprecedented PVCRs Enabling Compact SRAM Design—Part I: Device Concept

Tunnel diodes (TDs) and resonant tunneling diodes (RTDs) with negative differential resistance (NDR) have attracted interest in implementing high-density, low-power circuits, such as static random access memory (SRAM). However, the low peak-to-valley current ratios (PVCRs) in these devices cause high static leakage currents, leading to poor performance in the circuits and limiting their application. This article presents a novel device, i.e., a cross-coupled gated tunneling diode (XTD), that exhibits NDR with PVCRs exceeding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula> . The device design is validated by TCAD simulation as well as an experimental demonstration. In contrast to conventional TDs, which operate in the forward bias direction, the XTD operates in the reverse bias direction, thus suppressing thermionic emission and trap-assisted tunneling (TAT) currents, which together allow for the large PVCR. In Part II of this article, we continue to discuss compact, low-power SRAM cells based on the XTD.

Cross-Coupled Gated Tunneling Diodes With Unprecedented PVCRs Enabling Compact SRAM Design—Part II: SRAM Circuit

In Part I of this article, we present a novel device, i.e., a cross-coupled gated tunneling diode (XTD), which exhibits negative differential resistance (NDR) with peak-to-valley current ratios (PVCRs) exceeding 105. In this part of this article, based on the XTD, we introduce a compact static random access memory (SRAM) cell using a one-transistor and two-XTD (1T-2X) design. The layout of the SRAM cell as well as a detailed analysis of the cell behavior and SRAM array performance are presented. In particular, our simulation results show that the 1T-2X SRAM cell can achieve <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$70\times $ </tex-math></inline-formula> improvement in standby power with ~ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times $ </tex-math></inline-formula> area reduction compared to standard CMOS SRAM.

Observation of Controllable Negative Differential Resistance Behaviors through Morphology‐Dependent Zinc Oxide/p‐Si Heterointerface Structures

AbstractNegative differential resistance (NDR) has received considerable attention owing to the unique switching property, which exhibits an n‐shaped current–voltage curve without a monolithic increase in current as of the applied voltage bias increases. Nevertheless, various issues in previously reported NDR devices need to be addressed, such as complex manufacturing processes, operational instability, and difficulties in large‐area processing. In addition, methods for generating and controlling NDR have not yet been developed. This paper presents the findings of morphology‐dependent NDR in which three types of zinc oxide (ZnO) build a junction with p‐Si in the form of small nanoparticles, large nanoparticles, and films. The principle of NDR behaviors is elucidated through a comprehensive study, including an analysis of the energy band structure, morphological investigation, and electrical characterization, offering control of the peak‐to‐valley current ratio (PVCR). The highest PVCR = 4.96 A A−1 is obtained in the quantum dot ZnO/p‐Si structure and the NDR characteristics occur without external stimuli, such as irradiating light, cryogenic temperatures, or controlled atmospheres.

Analytical Modeling and Band-Structure Engineering of Resonant Tunneling Diode for Biased Terahertz Detector

A new strategy to significantly enhance the nonlinearity of double-barrier resonant tunneling diode (RTD) in the positive differential resistance region is theoretically proposed and experimentally demonstrated. An analytical model containing physical insight into the resonant tunneling process is established to bridge the nonlinearity of the current–voltage curve and the band-structure information of RTD. It intuitively shows that the intrinsic current responsivity of RTD as well as its nonlinearity can be greatly improved via band-structure engineering, as enhancing the resonant energy level of the well and reducing the current before the resonant tunneling process. The validation of the proposed model and the associated band-structure engineering strategy are verified by both device simulation and experiments. A RTD device with intrinsic current responsivity of 6.74 A/W is realized, while the peak-to-valley current ratio (PVCR) is also as large as 8.92. This method provides a new pathway to design high-performance terahertz (THz) detectors using double-barrier RTD and may share new perspective on the potential of RTD-based THz transceivers.