High-speed Electronic Devices Research Articles

Supercarbon assembly inspired two-dimensional hourglass fermion.

By using a tight-binding model, first-principles calculations, and abinitio molecular dynamics simulations, we theoretically demonstrate that the C76-Td-assembled two-dimensional (2D) honeycomb lattice is stable at room temperature and is resistant to mechanical deformation. We disclose that each C76-Td mimics a single carbon atom (geometrically and electronically); hence, it plays the role of one supercarbon. This inspires that the 2D material exhibits an exotic hourglass-like fermion at the Fermi level. Furthermore, we suggest that biaxial strains could modify the hourglass shape, including the electronic Fermi velocity, and induce magnetization. Hexagonal boron nitride can be employed as a protective layer without affecting the electronic structure of this material. This hourglass fermion has the potential to serve as a promising material for high-speed electronic devices and to bridge the gap between zero-dimensional spherical carbon clusters and two-dimensional graphene.

A new carbon allotrope with high carrier mobility and optical absorption.

Carbon atom has different bonding modes, which provides the possibility for the existence of multilayer carbon allotropes. Among these bonding modes, the sp3 hybrid bonding mode often causes atoms to be noncoplanar. This provides the possibility for the emergence of two-dimensional (2D) multilayer materials. In this work, a new 2D multilayer carbon allotrope named trilaminar buckled T-graphene is proposed. Carbon atoms have sp2 and sp3 hybridization in this structure. It is nonmagnetic and has an indirect band gap of 1.70 eV. It has mechanical stability and dynamic stability, and formation energy calculations also prove that it is stable. Thermal stability calculations results indicate that it does not change the bonding pattern at 1000 K. It is an elastically soft material with a low value of elastic constants. This structure shows amazing electrical properties, which has a high hole mobility of close to 3071 cm2 V-1 s-1. Optical property calculations results show that it has an optical gap of 1.70 eV and an ultrahigh absorption in visible and near ultraviolet light. Considering all its properties, this structure has great application potential in high-speed electronic and optoelectronic devices, optical filters, modified substrates, and adsorption sensors.

Comparison of essential physical properties between pristine armchair silicene nanoribbons and those doped with Ge and As

In this paper, some physical properties of pristine armchair silicene nanoribbons (ASiNR) and those doped with Ge (ASiGeNR) and As (ASiAsNR) using the VASP (Vienna ab initio simulation package) computational program, by using density functional theory. The results show significant differences in the structural and electronic properties between these systems. For ASiGeNR and ASiAsNR, structural parameters such as the distance between two nearest-neighbor atoms in the hexagonal ring, the distance between two farthest atoms, and the buckling height are all larger compared to ASiNR. While ASiNR and ASiGeNR have band gaps of approximately 0.262 eV and 0.2410 eV, respectively, opening at the Γ point, ASiAsNR does not have a band gap. The results indicate that ASiNR and ASiGeNR exhibit semiconductor properties, while ASiAsNR exhibits metallic properties. For ASiGeNR, the substitution of Ge leads to a reduction in bandgap and an increase in thermal conductivity, attributed to the energy level of Ge being close to that of Si. For ASiAsNR, the substitution with As increases the density of states at the top of the valence band, suggesting better electrical conductivity. ASiNR, with its wide bandgap, is suitable for applications in semiconductor devices such as MOSFETs and sensors. ASiGeNR is well-suited for optoelectronic applications such as solar cells or light-emitting diodes (LEDs), while ASiAsNR is appropriate for spintronics or high-speed electronic devices.

Nanosecond electric pulse-induced ultrafast piezoelectric responses in Co3+ substituted BiFeO3 epitaxial thin films

Understanding the ultra-fast dynamics of ferroelectric materials is essential for advancing the development of next-generation high speed electronic and photonic devices. Here, the ultrafast piezoelectric response of cobalt-substituted BiFeO3 (BiFe1-xCoxO3) with x = 0.15, consisting of morphotropic phase boundary of monoclinic MC and MA –type phases is investigated. The real-time piezoelectric response in (001)-oriented BiFe0.85Co0.15O3 (BFCO) epitaxial thin film was monitored using the time-resolved X-ray microdiffraction technique under an applied electric field with pulse widths 70 ns and 100 ns. The BFCO thin film yielded a high piezoelectric strain of approximately 0.53 % along [001] direction, with a giant c/a ratio (∼ 1.26) at an electric field of 1.3 MV/cm and a pulse width of 100 ns, with a piezoelectric coefficient of 40 pm/V. This finding is an important step towards the development of a high performance lead-free piezoelectric material for ultrafast operations in advanced technological applications.

Enhanced thermal conductivity and dielectric property of polyphenylene oxide/SiO2 composite by adding functional boron nitride strategy

Polymer composites with high thermal conductivity and excellent dielectric properties are ideal materials for high-speed electronic devices used in information processing. In this work, a high-speed microwave composite is designed by incorporating functional boron nitride (f-BN) into the polyphenylene oxide (PPO)/vinyl trimethoxysilane modified SiO2 (V-SiO2) composite. The dispersion of BN was significantly improved through surface coating followed by covalent modification. Adding f-BN into the PPO/V-SiO2 composite significantly enhances its dielectric properties and thermal conductivity, resulting in a lower dielectric constant (3.06–3.24) and dielectric loss (2.2×10−3@10 GHz). An effective thermal conductivity path is established by an optimal interface combination of f-BN and the PPO/V-SiO2 composite at a f-BN content of 15 wt%, the thermal conductivity of the composite reaches 0.858 W/(m·K). Moreover, the composite exhibits high thermal stability, low moisture absorption (<0.36 %), and possesses lightweight and flame retardant characteristics. This research provides a novel approach for PPO-based composites in high-speed devices and demonstrates the promising potential for applications in high-frequency substrates.

Modulation of electronic structures and transport properties in 2D TM0.5Ga1.5O3 (TM = Al, Ga, In)

In this study, the band structures, density of states and transport properties of two-dimensional (2D) TM0.5Ga1.5O3 (TM=Al, Ga, In) are investigated by the first principle and the deformation potential theory. Both 2D Al0.5Ga1.5O3 and 2D In0.5Ga1.5O3 alloys tend to form under poor-oxygen conditions. Compared to bulk Ga2O3, the bandgap of 2D Ga2O3 is increased by 0.382 eV and its electron mobility is significantly increased from 143.352cm2·V−1·s−1 to 1486.638cm2·V−1·s−1. For 2D Al0.5Ga1.5O3, the bandgap and the electron effective mass are larger than those of 2D Ga2O3, but its electron mobility is reduced by >25%. In contrast, the bandgap of 2D In0.5Ga1.5O3 is narrower than that of 2D Ga2O3 while its electron mobility is increased by >52%, reaching 2262.901cm2·V−1·s−1. Therefore, 2D In0.5Ga1.5O3 has great potential to be used as a transport material for high-speed Ga2O3 electronic devices.

Excellent Hole Mobility and Out-of-Plane Piezoelectricity in X-Penta-Graphene (X = Si or Ge) with Poisson's Ratio Inversion.

Recently, the application of two-dimensional (2D) piezoelectric materials has been seriously hindered because most of them possess only in-plane piezoelectricity but lack out-of-plane piezoelectricity. In this work, using first-principles calculation, by atomic substitution of penta-graphene (PG) with tiny out-of-plane piezoelectricity, we design and predict stable 2D X-PG (X = Si or Ge) semiconductors with excellent in-plane and out-of-plane piezoelectricity and extremely high in-plane hole mobility. Among them, Ge-PG exhibits better performance in all aspects with an in-plane strain piezoelectric coefficient d11 = 8.43 pm/V, an out-of-plane strain piezoelectric coefficient d33 = -3.63 pm/V, and in-plane hole mobility μh = 57.33 × 103 cm2 V-1 s-1. By doping Si and Ge atoms, the negative Poisson's ratio of PG approaches zero and reaches a positive value, which is due to the gradual weakening of the structure's mechanical strength. The bandgaps of Si-PG (0.78 eV) and Ge-PG (0.89 eV) are much smaller than that of PG (2.20 eV), by 2.82 and 2.47 times, respectively. This indicates that the substitution of X atoms can regulate the bandgap of PG. Importantly, the physical mechanism of the out-of-plane piezoelectricity of these monolayers is revealed. The super-dipole-moment effect proposed in the previous work is proved to exist in PG and X-PG, i.e., it is proved that their out-of-plane piezoelectric stress coefficient e33 increases with the super-dipole-moment. The e33-induced polarization direction is also consistent with the super-dipole-moment direction. X-PG is predicted to have prominent potential for nanodevices applied as electromechanical coupling systems: wearable, ultra-thin devices; high-speed electronic transmission devices; and so on.

Liquid phase exfoliation of few-layer borophene with high hole mobility for low-power electronic devices

Borophene, the two-dimensional allotrope of boron, has garnered significant interest in recent years due to its exceptional electronic, mechanical, and optical properties. In this work, an environment-friendly green approach has been utilized to synthesize p-type borophene, which consists of few layers as evidenced by electron and atomic force microscopic images. The Raman analysis indicated that these borophene layers possess β12 and χ3 phases. The photoemission spectra of these samples exhibit single exponential decay with a long lifetime of 7.2 µsec, showcasing its potential as a phosphorescent material in optoelectronics and quantum technologies. The photo-sensing capability of borophene was investigated by fabricating a Si/SiO2/Borophene/Ti/Pt photo-detector, which achieved an external quantum efficiency of 31 %, maximum photo responsivity of 200 mAW−1 and detectivity of 8.7x1011 Jones. Hall effect van der Pauw measurements revealed the p-type conductivity of the borophene film, along with a high hole mobility of 931.44 cm2V-1s−1 and a charge carrier density of 2 x 1012 cm−3, rendering these layers suitable for high-speed and low power electronic devices. This work emphasizes the importance of novel 2D materials like borophene with exceptional optoelectronic characteristics for developing future low-power electronic devices with remarkable performance.

Low-complexity continuous-variable quantum key distribution with true local oscillator using pilot-assisted frequency locking

In the domain of continuous variable quantum key distribution (CV-QKD), a significant challenge arises in achieving precise frequency synchronization, an issue commonly termed as frequency locking. This involves matching the optical frequencies of both the quantum signal laser and the local oscillator laser for accurate symbol demodulation during the exchange of quantum keys. As such, implementations today still grapple with maintaining precise synchronization between sender and receiver frequencies, occasionally hindering the efficiency and reliability of the information exchange. Addressing this challenge, we present and empirically validate a novel approach to CV-QKD by incorporating a pilot tone-assisted frequency locking algorithm to enhance stability when using a locally generated local oscillator (LLO) at the receiver. The proposed design leverages software-based optimization techniques, thereby eliminating the need for high-speed electronic stabilization devices and achieving efficient performance at typical repetition rates. Specifically, the introduction of the pilot tone algorithm allows us to effectively mitigate phase fluctuations and preserve the integrity of the quantum signals during transmission without resorting to time-multiplexed reference pulses or fast-locking electronics in the lasers. Our results suggest the potential for achieving secure key rates of up to 1 Mb/s over a 50 km single-mode fiber when using these techniques, offering promising insights into the feasibility of high-rate, low-complexity CV-QKD implementations under realistic conditions.

Molecular beam epitaxy growth and characterization of GePb alloys

Pb based group-IV alloys such as GePb have been gaining interest as a potential alternative for infrared detectors, quantum materials, and high-speed electronic devices. Challenges remain in their growth due to the extremely low solid solubility of Pb in the Ge–Pb system. This paper reports molecular beam epitaxy growth of GePb alloy thin films on Ge(100) substrates. Effusion cells of Ge and Pb are used to control the flux ratio independently. The optimal substrate temperature is found to be near the thermocouple temperature of 300 °C based on the characterization of the grown films using high-resolution x-ray diffraction. A large change in the Ge:Pb beam equivalent pressure ratio from 10:1 to 1:1 results in only a minimal increase of the Pb composition from 0.74% to 2.84% as estimated from Raman spectroscopy and Rutherford backscattering spectrometry. Scanning electron microscopy images show a large volume of Pb islands on the surface that form into either long trapezoidal rods or uniform droplets, with increasing Pb flux and growth time the density of Pb islands increased.

Graphene Devices for Aerial Wireless Communications at THz

This paper investigates the state-of-the-art of graphene-based technologies for the prospective use cases of end-to-end terahertz (THz) communication systems, such as industrial Internet of Things (IoT) applications and unmanned aerial vehicles (UAVs). THz communications offer ultra-high throughput and enhanced sensing capabilities, enabling advanced applications like UAV swarms and integrated sensing, localization, and mapping. The potential of wireless THz communication can be unlocked by graphene technology. Graphene, owing to its remarkable electrical, thermal, and mechanical properties, emerges as a promising candidate for a multitude of applications in aerial wireless communications in the THz band, including high-speed electronic devices, tunable metamaterials, and innovative antennas. However, reliable tools for the simulation-based design of graphene components, able to account for the fabrication-related uncertainties, are still missing. This paper presents the envisaged possibilities of wireless communications in THz bands, overviews graphene devices for RF applications at THz, and discusses the open issues of modelling THz devices and THz channel.

Research on electronic and optical properties of pristine and Ag/Au/Cu-doped graphene/MoS2 heterostructures

The Dirac cone in the single-layer graphene limits its application in electronic devices such as Schottky barrier diodes and field-effect transistors. Thus, we make the novel heterostructures based on graphene to solve this problem. The electronic and optical properties of pristine and Ag/Au/Cu-doped graphene/MoS2 heterostructures are investigated by using the density functional theory. For the Ag/Au/Cu-doped MoS2 monolayer, the results show that they are magnetic. Their bands across the Fermi level, which indicates these systems are metallic. For the Ag/Au/Cu-doped graphene/MoS2 heterostructures, they are metallic and nonmagnetic. Especially in the Au-doped graphene/MoS2, the Dirac cone opens about 66 meV. It means that Au-doped graphene/MoS2 has the potential to be a candidate material for high speed electronic devices. Compared with pristine heterostructure, the probability of electron transition in the low energy region is the enhanced in Ag/Au/Cu-doped systems. The optical absorption coefficient of doped heterostructure is enhanced in the range of 0–0.4 eV and 1.7–2.7 eV. This work indicates that these heterostructures have a certain potential in the application of nanodevices.

Low voltage-driven, high-performance TiO2 thin film transistors with MHz switching speed.

High-speed circuits based on thin film transistors (TFTs) show promising potential applications in biomedical imaging and human-machine interactions. One of the critical requirements for high-speed electronic devices lies in high-frequency switching or amplification at low voltages, typically driven by batteries (∼3.0 V). To date, however, most electrical performances of metal oxide TFTs are measured under direct current (DC) conditions, and their dynamic switching behaviour is scarcely explored and studied systematically. Here in this work, we present low voltage-driven, high-performance TiO2 thin film transistors, which can be operated at a switching speed of MHz. Our proposed TiO2 TFTs demonstrated a high on-off ratio of 107, together with a subthreshold swing (SS) of ∼150 mV Dec-1 averaged over four orders of magnitude, which can be further reduced below 100 mV Dec-1 when the temperature cools to 77 K. Additionally, the TiO2 TFTs exhibit excellent gate-pulse switching at various frequencies ranging from 1.0 Hz to 1.0 MHz. We also explored the potential application of the TiO2 TFTs as logic gates by constructing a resistive-loaded inverter, which shows stable operation at 10 kHz frequency and various temperatures. Thus, our results show the great potential of TiO2 TFTs as a new platform for high-speed electronic applications.

Direct growth of lattice mismatched InP on GaAs substrate with AlAs/GaAs superlattice-induced lateral quasi-quantum-wire buffer

With the technological importance, the demand on the infrared photonic and high-speed electronic devices is increasing in line with the needs for InP substrate which is used for the platform to grow the device structure. However, the InP substrate is not only limited to small diameter but also has poor mechanical hardness which are the bottleneck in reducing the device fabrication cost. In this regard, various methods are proposed to obtain InP template which grown on cheap and robust substrates as an alternative to replace the native InP substrate. In this article, we report an InP layer directly grown on GaAs substrate with the help of AlAs/GaAs superlattice-induced lateral quasi-quantum-wire buffer. The InP layer exhibited enhanced material quality with low defect density as a result of strain relaxation induced by the lateral quasi-quantum wires. This result can give insight into the alternative route to create large and robust InP template for low cost InP-based device applications.

Electronic properties by polarization-inducing of the F-GaN-H/SiC van der Waals hetero-structures

Atomic doping plays an important role in the fabrication of electronic devices. However, the atomic doping of two-dimensional materials is challenging as the thickness approaches the nanoscale. Self-doping, achieved through an asymmetric structure, can simplify the fabrication of electronic devices. In this study, the electronic properties of the F-GaN-H/SiC hetero-structures are investigated based on the first principles. The intrinsic polarization of the F-GaN-H leads to charge transfer resulting in self-doping. The spatial distribution of carriers in the F-GaN-H/SiC hetero-structures is reversed with polarization reversal. And p-type doped F-GaN-H and n-type doped SiC are achieved in polarization-down (Pd) hetero-structures, which is contrary to polarization-up (Pu) hetero-structures. The band gaps of the F-GaN-H/SiC hetero-structures are smaller than the intrinsic materials, and the band structures are modulated by polarization direction. For the Pu hetero-structures, a high hole mobility of 8.87 × 103 cm2 V−1 s−1 is achieved. The self-doping and the excellent transport properties of the F-GaN-H/SiC hetero-structures, with the tunable bandgap structures to polarization direction, not only simplify the fabrication of electronic devices but also demonstrate the potential application for optoelectronic and high-speed electronic devices.

Growth and characterization of Bi(110)/CrTe2 heterostructures: Exploring interplay between magnetism and topology

The interplay between topology and magnetism is vital for realizing exotic quantum phenomena, significant examples including quantum anomalous Hall effect, axion insulators, and high-order topological states. These states host great potential for future applications in high-speed and low-consumption electronic devices. Despite being extensively investigated, practical platforms are still scarce. In this work, with molecular beam epitaxy (MBE), we provide the first experimental report on high-quality Bi(110)/CrTe2 magnetic heterostructure. By employing in-situ high-resolution scanning tunneling microscopy, we are able to examine the interaction between magnetism and topology. There is a potential edge state at an energy level above the Fermi level, but no edge states observed near the Fermi level The absence of high-order topological corner states near E F highlights the importance of lattice matching and interface engineering in designing high-order topological states. Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.

Photonics-assisted joint radar detection and frequency measurement system

A photonics-assisted joint radar detection and microwave frequency measurement system is proposed. A broadband dual-chirp linear frequency-modulated (LFM) signal is generated based on an optically injected semiconductor laser, which is later shared by two functional modules. Thanks to the photonics-assisted broadband signal generation method, both radar detection with high resolution and microwave frequency measurement with high accuracy can be realized without using high-speed electronic devices. In the experiment, a two-dimensional resolution of 1.25 cm × 1.33 cm and a measurement error within ±50 MHz are achieved in radar detection and frequency measurement, respectively.

Recent Progress of Low Dielectric and High-Performance Polybenzoxazine-Based Composites.

With the rapid advancement of intelligent electronics, big data platforms, and other cutting-edge technologies, traditional low dielectric polymer matrix composites are no longer sufficient to satisfy the application requirements of high-end electronic information materials, particularly in the realm of high integration and high-frequency, high-speed electronic communication device manufacturing. Consequently, resin-based composites with exceptional low dielectric properties have garnered unprecedented attention. In recent years, benzoxazine-based composites have piqued the interest of scholars in the fields of high-temperature-resistant, low dielectric electronic materials due to their remarkable attributes such as high strength, high modulus, high heat resistance, low curing shrinkage, low thermal expansion coefficient, and excellent flame retardancy. This article focuses on the design and development of modification of polybenzoxazine based on low dielectric polybenzoxazine modification methods. Studies on manufacturing polybenzoxazine co-polymers and benzoxazine-based nanocomposites have also been reviewed.

Graphene-based field-effect transistor using gated highest-k ferroelectric thin film

We report a graphene-based highest-k ferroelectric field-effect transistor (GFE-FET) in which few-layer graphene sheets (FLGS) act as a channel layer and highest-k ferroelectric like barium zirconium titanate/barium calcium titanate (BZT/BCT) acts as an insulating gate layer. The electrochemical and sol-gel method has been used to prepare the used good quality FLGS and excellent BZT/BCT ferroelectric materials. SEM, XRD, UV–Vis, FTIR, and Raman spectroscopy measurements were done to characterize the produced materials. In order to evaluate the mobility of the fabricated GFE-FET, FET was fabricated with BZT/BCT gate and FLGS on top of it as conducting channel. The resultant field-effect mobility obtained from the fabricated GFE-FET is approximately ∼1.72 × 104 cm2V–1s−1 with 103 on/off ratio. These results ensure potential applications in some future high-speed electronic devices.

AlGaN/GaN heterostructures for high power and high-speed applications

Abstract AlGaN/GaN heterostructures are one of the most promising semiconducting structures for fabricating high-speed and high-power electronic devices such as high electron mobility transistors and heterojunction bipolar transistors. Due to the lack of native substrates, these epitaxial structures are generally grown on foreign substrate materials such as sapphire, SiC and Si by using two-step growth techniques. In this paper, a few test structures along with TLM pads, FET structure, ohmic contacts and Schottky contacts have been fabricated on AlGaN/GaN heterostructure by photolithography, reactive ion etching, and e-beam metallization. Transmission line measurement has been used to calculate the sheet resistivity and contact resistance of ohmic pads. Current voltage measurement is used to test an FET structure of size 1 × 150 µm2 with a gate length of 4 µm and source to drain spacing of 5 µm.