High Voltage Electronic Devices Research Articles

Vulnerability of the Load Frequency Control Against the Network Parameter Attack

By integrating the communication-enabled high-voltage electronic devices into the supervisory control and data acquisition (SCADA) system, the smart grid achieves flexible, economic, controllable operations of remote and real-time electricity transmission and distribution. However, it has been widely recognized that the SCADA system is vulnerable to unprecedented cyberattacks. In this paper, we propose a novel attack, namely, a network parameter attack (NPA), on the physical parameter of the branch to affect the load frequency control. The idea is to modify the control signal sent to the thyristor-controlled series compensator (TCSC) device to change the reactance of the transmission line, thus, inflicting the grid frequency stability. We first provide a sufficient condition for NPA to cause frequency instability. To further provide more insights, we analyze the impact of NPA on frequency stability based on the eigenvalue sensitivity. The vulnerable transmission lines are screened out based on the error caused by the NPA on the eigenvalues. Furthermore, we develop a least-effort but maximum-impact attack strategy considering the attacker’s limited resources. Finally, we conduct extensive simulations to validate the effectiveness of the attack and evaluate its impact on the system’s operation.

High-Temperature Performance of AlN MESFETs With Epitaxially Grown n-Type AlN Channel Layers

We fabricated AlN metal semiconductor field effect transistors (MESFETs) with an epitaxially grown n-type AlN channel layer and characterized the temperature dependence of their device properties. As the temperature was varied from room temperature to 500°C, maximum drain current increased from 0.42 to 45 mA/mm and maximum transconductance increased from 0.05 to 4.5 mS/mm. This enhanced device performance with increasing temperature is attributed to increased carrier concentration in n-type AlN due to the large ionization energy of Si donors. Owing to a large Schottky barrier height of 2.08 eV for the Ni gate electrode/n-type AlN interface, reverse leakage current is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-{10}}$ </tex-math></inline-formula> A/mm at temperatures ranging from room temperature to 500°C. Off-state breakdown voltage is as high as 1720 V for gate-drain spacing of 16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> . These results indicate that AlN MESFETs are promising for high-voltage electronic devices operating at high temperature.

Preparations, properties and applications of gallium oxide nanomaterials – A review

AbstractGallium oxide (Ga2O3) is an important wide bandgap transparent conductive oxide with many excellent properties, which is widely used in many fields such as catalysis, electroluminescence, biology, and so on. This review mainly introduces the researches on the preparation, properties and applications of gallium oxide nanomaterials. Initially, the preparation of gallium oxide by hydrothermal method has been highlighted and the effects of hydrothermal conditions on the morphologies and sizes of the final products were summarized. Furthermore, the unique properties of gallium oxide in the fields of electricity, gas, heat, and biomedicine are introduced, and the excellent luminescent properties of gallium oxide are emphasized. Additionally, this review mainly introduces the applications of gallium oxide in the fields of catalysis, gas sensors, optoelectronic devices, high voltage electronic devices and biomedicine. Finally, the problems and shortcomings in current research on gallium oxide nanomaterials are discussed and the opinions and prospects are put forward for the future perspective of the research in gallium oxide nanomaterials.

Growth of α- and β-Ga2O3 epitaxial layers on sapphire substrates using liquid-injection MOCVD

Ga2O3, a wide-bandgap semiconductor material, offers a great potential for power and high-voltage electronic devices. We report on the growth of undoped α- and β-phase Ga2O3 using liquid-injection metal-organic chemical vapor deposition (LI-MOCVD) on sapphire substrates. Using the same precursor (gallium acetylacetonate) and deposition temperature of 700 °C, the phase selection was controlled by the sapphire substrate orientation, where the growth of α- and β-phase Ga2O3 was achieved on m- and c-plane surface, respectively. As deduced from x-ray diffraction, α-Ga2O3 films show epitaxial character, while β- Ga2O3 films exhibit highly textured structure. Oxygen flow was also found to have a strong impact on the phase purity of α-Ga2O3 for the flow rates examined. Optical and electrical properties of the layers grown at different oxygen flow rates were also studied systematically. LI-MOCVD growth of α-phase Ga2O3 layers at relatively high deposition temperature widens the high-temperature processing of the Ga2O3-based electronic and optoelectronic devices.

Accelerated Aging Stability of β-Ga2O3-Titanium/Gold Ohmic Interfaces.

Stable ohmic contacts are critical to enable efficient operation of high-voltage electronic devices using ultrawide bandgap semiconductors. Here we perform, for the first time, thermally accelerated aging of Ti/Au ohmic interfaces to (010) β-Ga2O3. We find that a heavily doped semiconductor, doped n-type by Si-ion implantation, treated with reactive ion etch (RIE), results in a low specific contact resistance of ∼10-5 Ω cm2 that is stable upon accelerated thermal aging at 300 °C for 108 h. The low resistance interface is due to thermionic field emission of electrons over an inhomogeneous barrier. Scanning/transmission electron microscopy indicates that the multi-layered structure and elemental distribution across the contact interface, formed during a 1 min 470 °C post-metallization anneal, do not change noticeably over the aging period. A ∼1 nm interfacial layer is observed by high-resolution microscopy at the Ti-TiOx/Ga2O3 interface on all samples exposed to RIE, which may contribute to their excellent stability. In addition, longer-range facet-like interfacial features are observed, which may contribute to the inhomogeneous barrier. In contrast, Ti/Au junctions to moderately doped (010) Ga2O3 made with no RIE treatment exhibit a high contact resistance that increases upon accelerated aging, along with a partially lattice-matched interface. The methods used here to understand the process, structure, and electrical property relationships for Ti/Au contact interfaces to β-Ga2O3 can be applied to assess and tune the stability of a variety of other oxide-semiconductor interfaces.

Field Emitters for Miniature High-Voltage Electronic Devices Operating in Technical Vacuum

We present the results of the development and study of the field emitters for high-voltage electronic devices operating in technical vacuum. The main attention is paid to estimating the possibilities of using distributed field emitters under the conditions of intense ion bombardment.

Optimization of multi-tip-shaped field emitters with bilayer protective coatings

The calculations needed to optimize the ordered multi-tip-shaped silicon field emitters with the two-layer protective metal-fullerene coatings intended for use in high voltage electronic devices operating in technical vacuum have been performed. The calculations are fulfilled using the COMSOL program. The influence of the morphology of the surface on the emission characteristics of the emitters is determined, including the needles height and radius of their vertices, and also the distance between needles. It has been shown that the emitters with an area of 0.2 cm2, operating under the conditions of partial mutual screening, can provide currents of several hundred milliamps for fairly high voltages.

Increase the threshold voltage of high voltage GaN transistors by low temperature atomic hydrogen treatment

High-electron-mobility transistors (HEMTs) based on AlGaN/GaN epitaxial heterostructures are a promising element base for the fabrication of high voltage electronic devices of the next generation. This is caused by both the high mobility of charge carriers in the transistor channel and the high electric strength of the material, which makes it possible to attain high breakdown voltages. For use in high-power switches, normally off-mode GaN transistors operating under enhancement conditions are required. To fabricate normally off GaN transistors, one most frequently uses a subgate region based on magnesium-doped p-GaN. However, optimization of the p-GaN epitaxial-layer thickness and the doping level makes it possible to attain a threshold voltage of GaN transistors close to Vth = +2 V. In this study, it is shown that the use of low temperature treatment in an atomic hydrogen flow for the p-GaN-based subgate region before the deposition of gate-metallization layers makes it possible to increase the transistor threshold voltage to Vth = +3.5 V. The effects under observation can be caused by the formation of a dipole layer on the p-GaN surface induced by the effect of atomic hydrogen. The heat treatment of hydrogen-treated GaN transistors in a nitrogen environment at a temperature of T = 250°C for 12 h reveals no degradation of the transistor’s electrical parameters, which can be caused by the formation of a thermally stable dipole layer at the metal/p-GaN interface as a result of hydrogenation.

Prospective field emitters for miniature high voltage electronic devices operating at technical vacuum conditions

Prospective field emitters for miniature high voltage electronic devices operating at technical vacuum conditions

Field emission of multitip silicon structures with protection coatings

(0.1–0.3 cm2) area multipoint silicon emitters with two-layer metal–fullerene coatings are studied. Field-emission sources that generate currents of several tens of milliamperes that are sufficient for several millimeter- and submillimeter-wavelength microwave sources and compact X-ray sources are developed. Stable operation of multitip silicon field emitters with two-layer metal–fullerene coatings in high-voltage electronic devices is demonstrated at relatively high current output under technical vacuum conditions.

Hydrogen Flux Influence on Homo-Epitaxial 4H-SiC Doping Concentration Profile for High Power Application

Doping incorporation and good uniformity along the wafer it is a mandatory for application in high voltage electronic devices. In this work the effect of the Hydrogen (H) flux position inside the reaction chamber on homo-epitaxial 4H-SiC growth process has been studied. Capacitance-Voltage and FT-IR analyses show as the different position of the gas injector affect the doping and thickness uniformity and profile. On the other hand, By Candela and AFM analyses no morphological or surface influence by Hydrogen flux position has been observed.

Innovative Field Emitters for High-Voltage Electronic Devices

We describe multitip field emitters with protective coatings, which were developed in Peter the Great St. Petersburg Polytechnic University. The coatings ensure long-term operation of the emitters under high currents and technical vacuum. Innovative multi-layer emitters composed of contacting nanolayers of materials with different work functions are presented as well. The possibility by using the developed emitters in high-voltage electronic devices is demonstrated.

Sputter yields in diamond bombarded by ultra low energy ions

Artificial diamond is an ideal material for high power, high voltage electronic devices, and for engineering use in extreme environments. Diamond process development requires parallel development in characterization techniques such as ultra low energy SIMS (uleSIMS), especially in the ability to depth profile for impurities and dopants at high depth resolution. As a contribution to the background knowledge required, we have measured the sputter yields of single crystal high pressure high temperature (HPHT) diamond using O 2 +, Cs + and Ar + primary ions in the energy range 300 eV to 2 keV. We compare these with yields for silicon and GaAs. We show that the erosion rates with oxygen are ∼10 times what would be expected from ballistic processes and essentially energy independent in the measured range. This result agrees with the anomalously high sputter yield observed in the ion etching context. Conversely, positive ion yields for elements such as boron are very low in comparison with silicon. This points to a reactive ion etching process liberating CO or CO 2 rather than sputtering as the principal erosion process. This is both problematic and beneficial for SIMS analysis. Oxygen can be used to reach buried structures in diamond efficiently, and the effects of the near-normal incidence beam are planarizing as they are in silicon. Conversely, since positive ion yields are low, alternative probes or strategies must be found for high sensitivity profiling of electropositive elements.

Interconnected fibre masses precipitated from solutions of polymers

IN studies to increase the mechanical strength of polymeric encapsulants for high voltage electronic devices we have formed fibre masses of unusual structure from isotactic polypropylene. The method for producing these three-dimensionally interconnected fibrous structures is described here and involves agitation of a solution of the polymer at sonic frequencies with simultaneous cooling. This process has since been observed for polyethylene and polybutene-1. Furthermore, the process has been extended to other polymers, both crystalline and non-crystalline, through a process we call ‘seeding’. Uniform reinforcement of encapsulating resins through the addition of high strength, short fibres, is not practical because of the complex shapes and numerous small interstices of the devices to be encapsulated. We therefore set out in 1973 to form fibres in situ by precipitation from low viscosity solutions which would readily impregnate a device of complex geometry. As a secondary objective, we hoped to polymerise the solvent to form a matrix around the fibres thereby producing a self-reinforced composite.