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A numerical algorithm is obtained for calculating the electron transmission function in an arbitrary potential field in cases of 1D and 2D on the basis of a numerical procedure of searching for the energy levels and eigenwave functions of stationary states. Results are compared to available analytical and numerical solutions. A twisted nanoribbon is investigated as a 2D nanostructure. It is proposed that the obtained results be applied to 2D translation invariant waveguides, in which constants of the propagation guided modes act as energy levels. [ABSTRACT FROM AUTHOR]

In this work, we report the experimental observation of the ballistic transport of condensed exciton-polaritons at room temperature in a one-dimensional whispering-gallery microcavity. Such coherent transport, initiated by the pronounced inter-particle interactions of polaritons, leads to the generation of two symmetric emission beams in the momentum (angular) space. By means of spatially filtered angle-resolved photoluminescence imaging spectroscopy, we were able to identify their origin and successfully rationalize these observations using the potential energy-to-kinetic energy conversion picture. The energy-dependent emission linewidth, as well as TM to TE inter-mode scattering, have also been discussed. [ABSTRACT FROM AUTHOR]

Ohm's law for electrical conduction in metals is one of the first concepts taught in any physics curriculum. It is perfectly adequate in almost all practical circumstances, but breaks down in some special, interesting cases. To observe such breakdowns, one requires extremely pure materials, which are rare and often difficult to produce. Excitingly, forefront materials research is leading to the discovery of more and more examples in which one can break the 'purity barrier' and explore non‐Ohmic transport. The rapid development of the field is seeing equally rapid developments in the understanding of exotic non‐Ohmic regimes, but this is not always a smooth progression. New layers of insight often involve reversing what have previously been regarded as established facts. Indeed, the interpretations given of experimental data in many papers published less than a decade ago would (or should!) be different today. The goal of this article is to give an entry‐level guide to some of the pertinent issues that have emerged from this intense decade of research, attempting to keep the style of the presentation as informal and non‐mathematical as is practical. Although source literature will be cited, no attempt will be made at comprehensive citation, so the paper should not be regarded as a review. Rather, an effort will be made to identify and explain some issues that the authors believe are important but not sufficiently emphasized in the literature to date. In that sense the paper should be regarded as a kind of opinion piece, with, hopefully, some didactic value to a reader with a solid grounding in traditional condensed matter physics. [ABSTRACT FROM AUTHOR]

As the traditional silicon-based CMOS technology advances into the nanoscale stage, approaching its physical limits, the Carbon Nanotube Field-effect Transistor (CNTFET) is considered to be the most significant transistor technology beyond Moore's era. The CNTFET has a quasi-one-dimensional structure so that the carrier can realize ballistic transport and has very high mobility. At the same time, a single CNTFET can integrate hundreds of nanowires as the conductive channels, enabling significant current transport capabilities even in low supply voltage, thereby providing a foundational basis for achieving nanoscale ultra-large-scale analog/logic circuits. This paper summarizes the development status of the CNTFET compact model and digital/analog/RF integrated circuits. The challenges faced by SPICE modeling and circuit design are analyzed. Meanwhile, solutions to these challenges and development trends of carbon-based transistors are discussed. Finally, the future application prospects of carbon-based integrated circuits are presented. [ABSTRACT FROM AUTHOR]

Abstract Luminescent nanothermometry emerges as a powerful tool for studying protein dynamics. This technique was employed to perform the first measurement of the temperature dependence of protein Brownian velocity, showcasing the illustrative example of enhanced green fluorescent protein (EGFP) across physiologically relevant temperatures (30−50 °C) and concentrations (40, 60, and 80 × 10−3 kg m−3). EGFP exhibited a concentration‐dependent decrease in Brownian velocity, from (1.47 ± 0.09) × 10−3 m s−1 to (0.35 ± 0.01) × 10−3 m s−1, at 30 °C, mimicking crowded cellular environments. Notably, the protein Brownian velocity increased linearly with temperature. These results demonstrate the suitability of concentrated suspensions for modeling intracellular crowding and validate luminescent nanothermometry for protein Brownian motion studies. Furthermore, the observed linear relationship between the logarithm of the protein Brownian velocity and concentration indicates that EGFP motion is not primarily driven by diffusion, but more of a ballistic transport.

As the traditional silicon-based CMOS technology advances into the nanoscale stage, approaching its physical limits, the Carbon Nanotube Field-effect Transistor (CNTFET) is considered to be the most significant transistor technology beyond Moore’s era. The CNTFET has a quasi-one-dimensional structure so that the carrier can realize ballistic transport and has very high mobility. At the same time, a single CNTFET can integrate hundreds of nanowires as the conductive channels, enabling significant current transport capabilities even in low supply voltage, thereby providing a foundational basis for achieving nanoscale ultra-large-scale analog/logic circuits. This paper summarizes the development status of the CNTFET compact model and digital/analog/RF integrated circuits. The challenges faced by SPICE modeling and circuit design are analyzed. Meanwhile, solutions to these challenges and development trends of carbon-based transistors are discussed. Finally, the future application prospects of carbon-based integrated circuits are presented.

The quantum transport properties of InAs nanowire field effect transistor (NWFET) have been calculated and analyzed depending on the surface trap concentrations. Surface traps can be either impurity atoms, dangling bonds or structural deformations. Here, we have left some In and As atoms unsaturated to obtain surface traps. Our calculations show that the on-state voltage increases as the surface trap concentration increases. Within an equivalent circuit model, we have found that the effective field mobility is as low as 250 cm²/V.s following with small transconductance value of 2.4 nS for our simulated device. This shows that surface traps significantly effect the benchmarking properties of InAs NWFET. [ABSTRACT FROM AUTHOR]

An acoustoelectric approach to neuron function is proposed that combines aspects of the widely accepted electrical-circuit-based Hodgkin–Huxley model for the generation and propagation of action potentials via electric polarization with mechanical models based on propagation via capillary waves. Explaining measured velocities of action potentials quantitatively, it also predicts the electrical tunability of highly anisotropic polarization packages that surf on the dynamic mechanical force field deforming the neuron membrane. It relies substantially on the local motion of dipoles formed by excess charges close to the inside surface of the neuron membrane, which in turn are anisotropically screened by water molecules in their hydration shell, thus modulating the strong electric field at the interface. As demonstrated on acoustic resonators of suspended nanowires fabricated out of amorphous dipolar silicon nitride, high electric fields combined with predominantly axial-strain modulation can cause transverse acoustoelectric polarization waves that propagate soliton-like with extremely low loss. In neurons, the modulation of electric polarization is confined in the nanometer-thin skin of a high electric field inside the neuron membrane and propagates phase-coherent along the axon as a lowest-order one-dimensional breathing mode, similar to transverse polarization pulses studied in nanowire resonators. Some experiments for the further manifestation of the model as well as topological protection of such breathing-mode polarization waves are discussed. [ABSTRACT FROM AUTHOR]

The thermal conductance of nanowires is an oft-explored quantity, but its dependence on the nanowire shape is not completely understood. The behaviour of the conductance is examined as kinks of varying angular intensity are included into nanowires. The effects on thermal transport are evaluated through molecular dynamics simulations, phonon Monte Carlo simulations and classical solutions of the Fourier equation. A detailed look is taken at the nature of heat flux within said systems. The effects of the kink angle are found to be complex, influenced by multiple factors including crystal orientation, details of transport modelling, and the ratio of mean free path to characteristic system lengths. The effect of varying phonon reflection specularity on the heat flux is also examined. It is found that, in general, the flow of heat through systems simulated through phonon Monte Carlo methods is concentrated into a channel smaller than the wire dimensions, while this is not the case in the classical solutions of the Fourier model.

One-dimensional carbon nanotubes (CNTs) are promising for future nanoelectronics and optoelectronics, and an understanding of electrical contacts is essential for developing these technologies. Although significant efforts have been made in this direction, the quantitative behavior of electrical contacts remains poorly understood. Here, we investigate the effect of metal deformations on the gate voltage dependence of the conductance of metallic armchair and zigzag CNT field effect transistors (FETs). We employ density functional theory calculations of deformed CNTs under metal contacts to demonstrate that the current-voltage characteristics of the FET devices are qualitatively different from those expected for metallic CNT. We predict that, in the case of armchair CNT, the gate-voltage dependence of the conductance shows an ON/OFF ratio of about a factor of two, nearly independent of temperature. We attribute the simulated behavior to modification of the band structure under the metals caused by deformation. Our comprehensive model predicts a distinct feature of conductance modulation in armchair CNTFETs induced by the deformation of the CNT band structure. At the same time, the deformation in zigzag metallic CNTs leads to a band crossing but not to a bandgap opening. [ABSTRACT FROM AUTHOR]

An indirect exciton is a bound state of an electron and a hole in spatially separated layers. Two-dimensional indirect excitons can be created optically in heterostructures containing double quantum wells or atomically thin semiconductors. We study theoretically the transmission of such bosonic quasiparticles through nanoconstrictions. We show that the quantum transport phenomena, for example, conductance quantization, single-slit diffraction, two-slit interference, and the Talbot effect, are experimentally realizable in systems of indirect excitons. We discuss similarities and differences between these phenomena and their counterparts in electronic devices.

A review of recently explored new effects in SOI nanodevices and materials is given. Recent advances in the understanding of the sensitivity of electron and hole transport to the tensile or compressive uniaxial and biaxial strains in thin film SOI are presented. The performance and physical mechanisms are also addressed in multi-gate Si, SiGe and Ge MOSFETs. The impact of gate misalignment or underlap, as well as the use of the back gate for charge storage in double-gate nanodevices and of capacitorless DRAMare also outlined.

Diodes are a basic component of electrical circuits to control the flow of charge, and geometric diodes (GDs) are a special class that can operate using ballistic or quasi-ballistic transport in conjunction with geometric asymmetry to direct charge carriers preferentially in one direction, enabling an electron ratcheting effect. Nanomaterials present a unique platform for the development of GDs, and silicon nanowire (NW)-based GDscylindrically symmetric but translationally asymmetric three-dimensional nanostructureshave recently been demonstrated functioning at room temperature. These devices can theoretically achieve a near zero-bias turn-on voltage and rectify up to THz frequencies. Here, we synthesize silicon NW GDs and fabricate single-NW devices from which significant changes in diode performance are observed from relatively minor changes in geometry. To elucidate the interplay between geometry and ballistic behavior, we develop a Monte Carlo simulation that describes the quasi-ballistic behavior of electrons within a three-dimensional NW GD. We examine the effects of doping level, temperature, and geometry on charge carrier transport, revealing the relationships between charge carrier mean free path (MFP), specular reflection at surfaces, and geometry on GD performance. As expected, geometry strongly influences performance by directing or blocking charge carrier passage through the nanostructure. Interestingly, we find that the blocking effect is at least as important as the directing effect. Moreover, within certain geometric limits, the diode behavior is less sensitive to the MFP than might be initially expected because of the short relevant length scales and importance of the blocking effect. The results provide guidelines for the future design of NW GDs and enable the prediction and interpretation of trends in experimental results. An improved understanding of quasi-ballistic transport is crucial to guiding future experiments toward realizing THz rectification for applications in high-speed data transfer and long-wavelength energy harvesting. [ABSTRACT FROM AUTHOR]

In this paper, we consider the transport properties of the class of limit-periodic continuum Schrödinger operators whose potentials are approximated exponentially quickly by a sequence of periodic functions. For such an operator H, and XH(t) the Heisenberg evolution of the position operator, we show the limit of 1/t XH(t) Ψ as t → ∞ exists and is nonzero for Ψ ≠ 0 belonging to a dense subspace of initial states which are sufficiently regular and of suitably rapid decay. This is viewed as a particularly strong form of ballistic transport, and this is the first time it has been proven in a continuum almost periodic non-periodic setting. In particular, this statement implies that for the initial states considered, the second moment grows quadratically in time. [ABSTRACT FROM AUTHOR]

GaN/AlN superlattice structures have potential for high electron mobility transistors (HEMTs) applications; however, nonequilibrium phonon transport mechanisms within the superlattice have not been systematically investigated. Therefore, we investigate in detail the non-Fourier thermal conductivity of superlattice structures in the perpendicular interface direction and in the parallel interface direction around the phonon BTE numerical solution in this paper, taking the kinetic parameter based on the first principle as the input parameter of the equations and based on the DOM numerical solution scheme. The study reveals that mode temperature non-equilibrium in superlattices arises from ballistic transport within the layers and interface scattering between the layers. The thermal conductivity (TC) of superlattices can be modulated by scale effects, and in superlattices with small thicknesses, phonons exhibit quasi-ballistic transport. The interface thermal resistance predominantly originates from contributions by acoustic phonon (AP) and the first optical phonon (OP1). With increasing interface density, the combined effects of interface scattering and boundary scattering lead to strong phonon scattering, resulting in a decrease in TC parallel to the interfaces. This work provides valuable insights into the thermal transport properties of GaN/AlN superlattice semiconductors and offers useful theoretical guidance for thermal management through phonon particle properties. [ABSTRACT FROM AUTHOR]

Realizing valley asymmetric transmission(VAT) for incoming valley unpolarized Dirac carriers across an electrostatically modulated confinement potential(ECP) step, which is located at the interface of the unipolar ( $n-n^{^{\prime}}$ ) junction in dual-gated Bernal-bilayer graphene(BBG), has caught growing attention because it provides a platform to study the valley polarizer. Such a junction, however, seems to preclude from supporting vanishing VAT. Based on the effective two-band Hamiltonian of BBG with wave matching approach, we demonstrate theoretically that VAT through the n / n ′ interface vanishes in the following conditions: (i) the disappearing electrostatically modulated interlayer potential difference(EPD), or (ii) the invariance condition of the sum or difference of ECPs and EPDs, which physically corresponds to the zero band offset of the conduction or valence band in the band alignment of $n-n^{^{\prime}}$ junction. Guided by this, it is worth mentioning that the we can derive simple, analytical valley-independent expressions for the reflection and transmission probabilities. When the same invariant conditions occur, our calculations further show the appearance of the nearly vanishing VAT for the four-band model in bilayer graphene with ‘Mexican hat’-like band. As a byproduct, we apply these findings to suggest the best design for the valley-dependent selection of momenta based on dual-gated BBG connected to two pristine BBG electrodes in which ECPs of the two outer regions are distinguishable and show that the sign of valley polarization can be switched via varying EPD. We expect our results can provide guidance for future device applications relying on ballistic and valley-selective transport.

In this work, we report the experimental observation of the ballistic transport of condensed exciton-polaritons at room temperature in a one-dimensional whispering-gallery microcavity. Such coherent transport, initiated by the pronounced inter-particle interactions of polaritons, leads to the generation of two symmetric emission beams in the momentum (angular) space. By means of spatially filtered angle-resolved photoluminescence imaging spectroscopy, we were able to identify their origin and successfully rationalize these observations using the potential energy-to-kinetic energy conversion picture. The energy-dependent emission linewidth, as well as TM to TE inter-mode scattering, have also been discussed.

Polymer-assisted wet transfer of chemical vapor deposited (CVD) graphene has achieved great success towards the true potential for large-scale electronic applications, while the lack of an efficient polymer removal method has been regarded as a crucial factor for realizing high carrier mobility in graphene devices. Hereby, we report an efficient and facile method to clean polymer residues on graphene surface by merely employing solvent mixture of isopropanol (IPA) and water (H2O). Raman spectroscopy shows an intact crystal structure of graphene after treatment, and the x-ray photoelectron spectroscopy indicates a significant decrease in the Câ€"O and C=O bond signals, which is mainly attributed to the removal of polymer residues and further confirmed by subsequent atomic force microscopy analysis. More importantly, our gated measurements demonstrate that the proposed approach has resulted in a 3-fold increase of the carrier mobility in CVD graphene with the electron mobility close to 10 000 cm2 Vâˆ'1 Sâˆ'1, corresponding to an electron mean free path beyond 100 nm. This intrigues the promising application for this novel method in achieving ballistic transport for CVD graphene devices. [ABSTRACT FROM AUTHOR]

Material challenges are the key issue in Majorana research, where surface disorder constrains device performance. Here, we tackle this challenge by embedding PbTe nanowires within a lattice-constant-matched crystal. The wire edges are shaped by self-organized growth instead of lithography, resulting in nearly atomically flat facets along both cross-sectional and longitudinal directions. Quantized conductance is observed at zero magnetic field with channel lengths maximally reaching 1.7 μm, significantly surpassing the state-of-the-art III-V nanowires (an order-of-magnitude improvement compared to InSb). Coupling PbTe to a Pb film unveils a flat interface spanning micrometers and a large superconducting gap of 1 meV. Our result not only represents a stride toward meeting the stringent low-disorder requirement for Majoranas, but may also open the door to various hybrid quantum devices requiring a low level of disorder.

In the recent past, due to ballistic transport capability, carbon nanotube field-effect transistors (CNTFETs) have emerged as a potential replacement to conventional semiconductor devices. However, the major bottleneck issue of appropriate CNT synthesis is still standing high, and the fabrication of CNTFETs is usually found possible with Ohmic or Schottky type contacts. This paper concentrates on Schottky barrier(SB) CNTFETs in which carriers' transmission coefficient is modulated at metal-CNT contact. The basic nature of metal contacted CNTFET devices is ambipolar, and it has been widely proved with the use of coupled Schrödinger–Poisson equation. However, it restricts the efficiency of CNTFETs in both active and cutoff regimes. This paper demonstrates the use of double-gate (DG) structure in CNTFETs to suppress ambipolarity in an efficient way. We have explicitly used the ant lion optimization technique to optimize Ion and Ioff current and established that the proposed enhanced-gate overlapping approach improves the performance characteristic of the CNTFETs. [ABSTRACT FROM AUTHOR]

High aspect ratio metal nanostructures are commonly found in a broad range of applications such as electronic compute structures and sensing. The self‐heating and elevated temperatures in these structures, however, pose a significant bottleneck to both the reliability and clock frequencies of modern electronic devices. Any notable progress in energy efficiency and speed requires fundamental and tunable thermal transport mechanisms in nanostructured metals. In this work, time‐domain thermoreflectance is used to expose cross‐plane quasi‐ballistic transport in epitaxially grown metallic Ir(001) interposed between Al and MgO(001). Thermal conductivities ranges from roughly 65 (96 in‐plane) to 119 (122 in‐plane) W m−1 K−1 for 25.5–133.0 nm films, respectively. Further, low defects afforded by epitaxial growth are suspected to allow the observation of electron–phonon coupling effects in sub‐20 nm metals with traditionally electron‐mediated thermal transport. Via combined electro‐thermal measurements and phenomenological modeling, the transition is revealed between three modes of cross‐plane heat conduction across different thicknesses and an interplay among them: electron dominant, phonon dominant, and electron–phonon energy conversion dominant. The results substantiate unexplored modes of heat transport in nanostructured metals, the insights of which can be used to develop electro‐thermal solutions for a host of modern microelectronic devices and sensing structures. [ABSTRACT FROM AUTHOR]

We propose a numerical compact model for describing the drain current in ballistic mode by using an expression to represent the transmission coefficients for all operating regions. This model is based on our previous study of an analytic compact model for the subthreshold region in which the DIBL and source-to-drain tunneling effects were both taken into account. This paper introduces an approach to establishing the smoothing function for expressing the critical parameters in the model's overall operating regions. The resulting compact model was tested in a TCAD NEGF simulation, demonstrating good consistency. [ABSTRACT FROM AUTHOR]

Schottky diode (SD) has seen great improvements in the past few decades and, for many THz applications, it is the most useful device. However, the use and recycling of forms of energy such as solar energy and the infrared thermal radiation that the Earth continuously emits represent one of the most relevant and critical issues for this diode, which is unable to rectify signals above 5 THz. The goal is to develop highly efficient diodes capable of converting radiation from IR spectra to visible ones in direct current (DC). A set of performance criteria is investigated to select some of the most prominent materials required for developing innovative types of electrodes, but also a wide variety of insulator layers is required for the rectification process, which can affect the performance of the device. The current rectifying devices are here reviewed according to the defined performance criteria. The main aim of this review is to provide a wide overview of recent research progress, specific issues, performance, and future directions in THz rectifier technology based on quantum mechanical tunneling and asymmetric structure. [ABSTRACT FROM AUTHOR]

The present studies deal with the catalytic character of carbon nanostructure (Graphene (Gr) and single-wall carbon nanotubes (SWNTs), and their composite versions) on the hydrogen sorption behavior of 1:2 Mg(NH 2) 2 –LiH/Li 4 BH 4 (NH 2) 3. The inclusion of an optimal quantity of 2 wt% SWNTs in Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 resulted in superior hydrogen sorption over 2 wt% Gr and 2 wt% of (Gr and SWNT) composite. The onset desorption temperature for SWNTs catalyzed Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 is 108 °C which is 32 °C, 44 °C lower compared to Gr catalyzed Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 and uncatalyzed Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 respectively. The de/re-hydrogenation kinetics of the SWNT catalyzed sample has been found to be 4.02 wt% and 4.63 wt% within 15min at 170 °C and 7 MPa H 2 pressure, correspondingly. The activation energy for SWNT catalyzed Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 has been found to be 69.75 kJ/mol. The SWNT catalyzed Mg(NH 2) 2 –2LiH/Li 4 BH 4 (NH 2) 3 shows good cyclic stability (almost no degradation) up to 10 cycles. The better hydrogen sorption for SWNTs is attributed to the ballistic transport of hydrogen atoms within and across the amide/hydride matrix. In contrast, Gr sheets agglomerate, which adversely affects hydrogen sorption from Gr and Gr+SWNT composites. A hydrogen sorption mechanism has been proposed based on structural, microstructural, Fourier-transform infrared spectroscopy, and Raman characterization results. The ballistic transport of SWNTs on the hydrogen sorption of 1:2 Mg(NH 2) 2 –LIH/Li 4 BH 4 (NH 2) 3. [Display omitted] • The inclusion of 2 wt% SWNTs in 1:2 Mg(NH 2) 2 –LiH/Li 4 BH 4 (NH 2) 3 has been shown to improve hydrogen sorption. • The onset desorption temperature for SWNTs catalyzed 1:2 Mg(NH 2) 2 –LiH/Li 4 BH 4 (NH 2) 3 is 108 °C. • SWNT catalyzed 1:2 Mg(NH 2) 2 –LiH/Li 4 BH 4 (NH 2) 3 activation energy was found to be 69.75 kJ/mol. • Up to 10 cycles, the SWNT catalyzed 1:2 Mg(NH2)2–LiH/Li4BH4(NH2)3 shows good cyclic stability. • SWNTs attributed to the ballistic transport of hydrogen atoms from and to the amide/hydride matrix. [ABSTRACT FROM AUTHOR]

To develop efficient thermal management strategies for wide-bandgap (WBG) semiconductor devices, it is essential to have a clear understanding of the heat transport process within the device and accurately predict the junction temperature. In this article, we use the phonon Monte Carlo (MC) method with the phonon dispersion of several typical WBG semiconductors, including GaN, SiC, AlN, and $\beta $ -Ga2O3, to investigate the thermal spreading resistance in a ballistic-diffusive regime. This work shows that when compared with Fourier’s law-based predictions, the increase in the thermal resistance caused by the ballistic effects is strongly related to the phonon dispersion. Based on the model derived under the gray-medium approximation and the results of dispersion MC, we obtained a thermal resistance model that can well address the issues of thermal spreading, ballistic effects, and the influence of phonon dispersion. The model can be easily coupled with finite-element method (FEM)-based thermal analysis and applied to different materials. This article can provide a clearer understanding of the influence of phonon dispersion on the thermal transport process, and it can be useful for the prediction of junction temperatures and the development of thermal management strategies for WBG semiconductor devices. [ABSTRACT FROM AUTHOR]

With advancements in nanomaterial synthesis, semiconductor device technology entered a new era with nanotechnology. In fact, quantum effects such as confinement and tunneling have played a significant role in device characteristics. In this work, we have investigated quantum ballistic transport properties of Si nanowire MOSFET (Si NWMOSFET) with 4 nm gate length. Since gate length is shorter than the electron wavelength in our Si NWMOSFET, ballistic transport in one dimension (1D) is expected to be the dominant mechanism for carrier transport. Therefore, the parameters which are crucial for efficient MOSFET operation such as gate length, temperature, gate voltage have been simulated using the density gradient method to present quantum confinement effect on device transfer characteristics. We have found that Si NWMOSFET has an Ion/Ioff ratio > 108, which is close to ideal value for similar nano MOSFETs. Moreover, due to short channel, intersubband scattering can deteriorate 1D ballistic transport properties of Si NWMOSFET, especially in low temperatures. [ABSTRACT FROM AUTHOR]

This article reports the temperature-dependent characterization and analysis of quasi-ballistic transport in fully depleted silicon-on-insulator (FD-SOI) metal-oxide-semiconductor field-effect-transistors (MOSFETs) from a 22-nm commercial CMOS technology. Measurements of current–voltage (${I}$ – ${V}$) characteristics for temperatures ranging from 10 up to 300 K are presented in this article. Key electrical parameters are extracted as a function of temperature, including threshold voltage, subthreshold swing, ON-state current, series resistance, mobility, mean free path, and ballistic ratio. An experimentally validated virtual source modeling approach that incorporates back-gate biasing is presented in this article for temperatures down to 10 K. A comparison with bulk devices reveals less reduction in ballisticity at low temperatures and is attributed to a smaller contribution from ionized impurity scattering due to lower doping in the fully depleted (FD) channel. [ABSTRACT FROM AUTHOR]

Junctions based on electronic ballistic waveguides, such as semiconductor nanowires or nanoribbons with transverse structural variations in the order of a large fraction of their Fermi wavelength, are suggested as highly efficient thermoelectric (TE) devices. Full harnessing of their potential requires a capability to either deterministically induce structural variations that tailor their transmission properties at the Fermi level or alternatively to form waveguides that are disordered (chaotic) but can be structurally modified continuously until favorable TE properties are achieved. Well-established methods to realize either of these routes do not exist. Here, disordered bismuth (Bi) waveguides are reported, which are both formed and structurally tuned by electromigration until their efficiency as TE devices is maximized. In accordance with theory, the conductance of the most efficient TE waveguides is in the sub quantum of conductance regime. The stability of these structures is found to be substantially higher than other actively studied devices such as single molecule junctions., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Hybrid devices that combine superconductors (S) and semiconductors (Sm) have attracted great attention due to the integration of the properties of both materials, which relies on the interface details and the resulting coupling strength and wavefunction hybridization. However, until now, none of the experiments have reported good control of the band alignment of the interface, as well as its tunability to the coupling and hybridization. Here, the interface is modified by inducing specific argon milling while maintaining its high quality, e.g., atomic connection, which results in a large induced superconducting gap and ballistic transport. By comparing with Schrödinger-Poisson calculations, it is proven that this method can vary the band bending/coupling strength and the electronic spatial distribution. In the strong coupling regime, the coexistence and tunability of crossed Andreev reflection and elastic co-tunneling-key ingredients for the Kitaev chain-are confirmed. This method is also generic for other materials and achieves a hard and huge superconducting gap in lead and indium antimonide nanowire (Pb-InSb) devices. Such a versatile method, compatible with the standard fabrication process and accompanied by the well-controlled modification of the interface, will definitely boost the creation of more sophisticated hybrid devices for exploring physics in solid-state systems., (© 2024 Wiley‐VCH GmbH.)

We discuss the numerical aspects of the Boltzmann transport equation (BE) for electrons in semiconductor devices, which is stabilized by Godunov's scheme. The k-space is discretized with a grid based on the total energy to suppress spurious diffusion in the stationary case. Band structures of arbitrary shape can be handled. In the stationary case, the discrete BE yields always nonnegative distribution functions and the corresponding system matrix has only eigenvalues with positive real parts (diagonally dominant matrix) resulting in an excellent numerical stability. In the transient case, this property yields an upper limit for the time step ensuring the stability of the CPU-efficient forward Euler scheme and a positive distribution function. Similar to the Monte-Carlo (MC) method, the discrete BE can be solved in time together with the Poisson equation (PE), where the time steps for the PE are split into shorter time steps for the BE, which can be performed at minor additional computational cost. Thus, similar to the MC method, the transient approach is matrix-free and the solution of memory and CPU intensive large systems of linear equations is avoided. The numerical properties of the approach are demonstrated for a silicon nanowire NMOSFET, for which the stationary I–V characteristics, small-signal admittance parameters and the switching behavior are simulated with and without strong scattering. The spurious damping introduced by Godunov's (upwind) scheme is found to be negligible in the technically relevant frequency range. The inherent asymmetry of the upwind scheme results in an error for very strong scattering that can be alleviated by a finer grid in transport direction. [ABSTRACT FROM AUTHOR]

We consider heat transport across a harmonic chain of charged particles, with transverse degrees of freedom, in the presence of a uniform magnetic field. For an open chain connected to heat baths at the two ends we obtain the nonequilibrium Green's function expression for the heat current. This expression involves two different Green's functions which can be identified as corresponding respectively to scattering processes within or between the two transverse waves. The presence of the magnetic field leads to two phonon bands of the isolated system and we show that the net transmission can be written as a sum of two distinct terms attributable to the two bands. Exact expressions are obtained for the current in the thermodynamic limit, for the the cases of free and fixed boundary conditions. In this limit, we find that at small frequency ω , the effective transmission has the frequency-dependence ω 3 / 2 and ω 1 / 2 for fixed and free boundary conditions respectively. This is in contrast to the zero magnetic field case where the transmission has the dependence ω 2 and ω 0 for the two boundary conditions respectively, and can be understood as arising from the quadratic low frequency phonon dispersion. [ABSTRACT FROM AUTHOR]

This article presents a Schrödinger–Poisson based technique to predict I−V characteristics of trigate Si fin field effect transistors (FinFETs). The channel characteristics are modeled by a three‐dimensional (3D) Schrödinger wave equation considering quantum‐mechanical ballistic transport. Using a nonequilibrium green function and a 3D Poisson equation, drain current associated with source‐drain Fermi energy difference is evaluated. Contact resistance and its impact on the drain current is adjusted using a modeled parameter in Fermi‐Dirac distribution function. It is observed that the drain current as a function of drain bias saturates because of the finite carrier supply from the source electrode. The model is calibrated using TCAD simulations for quantum transport. To validate the proposed model, output and transfer characteristics of nanoscale FinFETs are compared with experimental data and a good degree of accuracy is observed. It has been demonstrated that the proposed model has the ability to predict FinFETs characteristics having Tfin=3−35nm. [ABSTRACT FROM AUTHOR]

As the lightest two-dimensional (2D) metal, borophene was rarely applied in semiconductor devices. The recently synthesized hydrogenated borophene (B8H4) opens up the possibility for 2D boron-based semiconductors. Here, by first-principles calculations, we evaluate the potential application of B8H4 in nanoscale field-effect transistors (FETs). We disclose the tunable electronic properties of monolayer B8H4 under strain engineering and the promising electrical performance of B8H4-based FETs in the ballistic transport regime. We also reveal that pristine B8H4-FETs can fulfill the ITRS (International Technology Roadmap for Semiconductors) requirement for high-performance devices with 5 nm channel length in terms of on-current, delay time, and power-delay product. Moreover, 5% biaxial compressive strain can further scale B8H4-FETs down to 3 nm gate length. This study unveils the potential applications of B8H4 in sub-5 nm FETs and underlines the promising role of boron-based semiconductors in future nanoelectronics. [ABSTRACT FROM AUTHOR]

The influence of spatial variation of Fermi velocity on the spin-polarized transport properties of massless Dirac fermions in proximity-induced ferromagnetic graphene junction was investigated. We found that the velocity ratio ξ causing the width of the spin conductance dip near the Dirac point is broadened as the Fermi velocity ratio increases. In contrast, the effect of the Fermi velocity mismatch does not affect the shifting of the Dirac point. It leads to the indirect measurement of the Fermi velocity ratio that can be tuned by the spin-dependent conductance. In addition to the presence of both the exchange field and the Fermi velocity modulation, we found high spin filtering occurs when the Fermi velocity ratio ξ ≥ 1. Due to the transmission probability of electron with spin down, T↓ is blocked by the effect of Fermi velocity modulation similar to waves travelling through a different media. Moreover, we also found that the resonant transmission of the electron with spin up can be perfectly transmitted through the Fermi velocity barrier at the limit injected angle θ → π/2 for H/EF ≈ 1. The spin transport properties can be controlled by suitably modifying the strength of the ferromagnetic insulator and varying the Fermi velocity modulation, which leads to the highest spin polarization. By manipulating the behavior of spin-dependent collimation and spin beam splitting in this structure, we proposed a spin transport device for making lateral spin polarization. These interesting features will help make the development of spintronic devices in the graphene-based nanostructure. [ABSTRACT FROM AUTHOR]

The performance of two-dimensional (2D) monolayer GaN Schottky barrier field effect transistors (SBFETs) with four different metals (Ag, Au, Al, and Pt) as electrodes were studied by using ab initio simulations. The N-type Schottky contact is formed on Ag-GaN, Au-GaN, and Pt-GaN, characterized by electron Schottky barrier heights (SBH) of 0.6, 0.5, and 0.38 eV, respectively. Whereas, Al-GaN contact formed P-type Schottky contact with hole SBH of 1.42 eV. The 5.1 nm GaN SBFETs with four metal electrodes all could overcome the short-channel effect. Additionally, GaN SBFETs with Ag and Au electrodes have excellent performance, whose ON-currents are 1151.1 μA/μm and 1258.9 μA/μm, respectively. They could satisfy the demands of International Technology Roadmap for Semiconductors for high-performance transistor. Furthermore, research indicates that the device's current increases with increasing temperature. Notably, under the constant bias and gate voltage, the current is unaffected by temperature variations between the left and right electrodes. • 2D GaN SBFETs with four different metals (Ag, Au, Al, and Pt) as electrodes. • All SBFETs could meet the OFF-state requirement of ITRS. • GaN SBFETs with Ag and Au as electrodes have excellent performance (ON-state current, C g , DPI, τ, and SS). • The current value and the temperature difference of electrodes are not correlated. [ABSTRACT FROM AUTHOR]

We postulate that in ultra-scaled Field Effect Transistors (FET), such as nanowires in sub7nm technology, the source contact will act as an energy filter and increase the effective temperature of carriers arriving at the channel barrier. This is due to the absence of inelastic scattering in the short source-contact-to-channel region. As a result, the Sub-threshold Slope (SS) will increase substantially. In this paper, we verify this energy filtering effect through numerical calculations and Technology ComputerAided-Design (TCAD) simulations calibrated to quantum solvers for electrostatics. It is found that SS degradation increases as the source metal workfunction increases. At 300K, in the nanowire simulated, SS increases from 94mV/dec to 109mV/dec for gate length, LG, = 10 nm and from 72mV/dec to 88mV/dec for LG = 15 nm, representing an increase of effective carrier temperature from 300K to more than 340K. The simulation result is also verified by including the Schroedinger equation (SE) for tunneling in TCAD simulation. It is also found that such an effect is worse at higher device temperature and disappears at cryogenic temperature.

Abstract This paper presents a physically valid quasi-ballistic drain current model applicable for nanoscale symmetric Double Gate (SDG) MOSFETs. The proposed drain current model includes both diffusive and ballistic transport phenomena. The model considers the important positional carrier scattering dependency effect near the source region described in terms of transmission and reflection co-efficients related to the scattering theory. The significance of carrier transport near the bottleneck source region is illustrated where the carriers diffuse into the channel at a relatively lower velocity before accelerating ballistically. The results obtained demonstrate carrier scattering dependency at the critical layer defined near the low field source region on the drain current characteristics. The proposed model partly evolves from Natori’s ballistic bulk MOSFET model that is modified accordingly to be valid for a symmetric Double Gate MOSFET in the nanoscale regime. Carrier degeneracy and Fermi–Dirac statistics are included in the work so as to justify the complete physicality of the model. The model is further extended and is shown to be continuous in terms of terminal charges and capacitances in all regions of operation. A comparative analysis is also done between the proposed quasi-ballistic model and a hypothetical complete ballistic device.

The trend toward miniaturization of electronic devices has increased the interest in nano scale heat transport, particularly, in laser-excited solids where electron–electron thermalization and electron-phonon coupling play a key role. Using a multi-temperature hyperbolic model, which takes into account the coupling between initially non-thermalized electrons and different phonon branches, we obtain a hierarchy of heat conduction equations for the electron temperature, which arises due to multi-length and time scales nature of coupling between different excitations. The hierarchy predicts that the ultrashort laser pulse induces a multi-front temperature wave propagating into the bulk of the material, which includes various heat transport regimes, ranging from the ballistic motion of the initially non-thermalized electrons propagating on the shortest time scale without interaction with the lattice as a temperature discontinuity, to the continuous wave-like temperature fronts arising on the intermediate time scale due to coupling between various excitations, and eventually to the classical Fourier transport on the longest time scale. The model is expected to be useful for modeling heat wave propagation phenomena in heterostructures and metamaterials. [ABSTRACT FROM AUTHOR]

In conductors with a very low defect density, electrons at low temperatures collide mainly with the sample edges; therefore, the ballistic transport of charge and heat is implemented. An applied perpendicular magnetic field significantly modifies ballistic transport. For the case of two-dimensional electrons, in magnetic fields at which the diameter of cyclotron trajectories is smaller than the sample width, the hydrodynamic transport regime forms. In this regime, the flow is mainly controlled by rare electron–electron collisions, which determine the viscosity effect. In this work, we study the ballistic flow of two-dimensional electrons in long samples in magnetic fields up to the critical field of the transition to the hydrodynamic regime. By solving the kinetic equation, we obtain analytical formulas for the current density and the Hall electric field far and close to the ballistic–hydrodynamic transition, as well as for the longitudinal and Hall resistances in these ranges. Our theoretical results apparently describe the observed longitudinal resistance of pure graphene samples in the magnetic-field range below the ballistic–hydrodynamic transition. [ABSTRACT FROM AUTHOR]

The terahertz (THz) technology has found applications ranging from astronomical science and earth observation to compact radars, non-destructive testing, chemical analysis, explosive detection, moisture content determination, coating thickness control, film uniformity determination, structural integrity testing wireless covert communications, medical applications (including skin cancer detection), imaging, and concealed weapons detection. Beyond 5G Wi-Fi and Internet of Things (IoT) are the expected killer applications of the THz technology. Plasmonic TeraFETs such as Si CMOS with feature sizes down to 3 nm could enable a dramatic expansion of all these applications. At the FET channel sizes below 100 nm, the physics of the electron transport changes from the collision dominated to the ballistic or quasi-ballistic transport. In the ballistic regime, the electron inertia and the waves of the electron density (plasma waves) determine the high frequency response that extends into the THz range of frequencies. The rectification and instabilities of the plasma waves support a new generation of THz and sub-THz plasmonic devices. The plasmonic electronics technology has a potential become a dominant THz electronics sensing technology when the plasmonic THz sources join the compact, efficient, and fast plasmonic TeraFET THz detectors already demonstrated and being commercialized. [ABSTRACT FROM AUTHOR]

FinFET and fully depleted silicon-on-insulator (FDSOI) structures could further improve transistor's performance and, however, also introduce some new problems, especially the increasingly severer self-heating effect (SHE). In this paper, by utilizing the ultra-fast sub-1 ns measurement technique, I-V characteristics of FinFETs and FDSOI devices at different switch speeds are obtained. Furthermore, dynamic SHE phenomena as well as the time-resolved channel temperature change during transistor's switch on and off are able to be experimentally observed. And, more accurate device parameters like ballistic transport efficiency are extracted by the ultra-fast measurements. Moreover, it is experimentally confirmed that several nanoseconds are required to heat up the channel of transistors by the direct electrical characterization and, therefore, in sub-10 nm devices, SHE might be alleviated under high frequency/speed operations.