Simulation Study of the Use of AlGaN/GaN Ultra-Thin-Barrier HEMTs with Hybrid Gates for Achieving a Wide Threshold Voltage Modulation Range

In this work, novel hybrid gate Ultra-Thin-Barrier HEMTs (HG-UTB HEMTs) featuring a wide modulation range of threshold voltages (VTH) are proposed. The hybrid gate structure consists of a p-GaN gate part and a MIS-gate part. Due to the depletion effect assisted by the p-GaN gate part, the VTH of HG-UTB HEMTs can be significantly increased. By tailoring the hole concentration of the p-GaN gate, the VTH can be flexibly modulated from 1.63 V to 3.84 V. Moreover, the MIS-gate part enables the effective reduction in the electric field (E-field) peak at the drain-side edge of the p-GaN gate, which reduces the potential gate degradation originating from the high E-field in the p-GaN gate. Meanwhile, the HG-UTB HEMTs exhibit a maximum drain current as high as 701 mA/mm and correspond to an on-resistance of 10.1 Ω mm and a breakdown voltage of 610 V. The proposed HG-UTB HEMTs are a potential means to achieve normally off GaN HEMTs with a promising device performance and featuring a flexible VTH modulation range, which is of great interest for versatile power applications.

Mechanical Characteristics and Energy Evolution of Sandstone Three-Point Bending Test

With the increase of underground mining depth in coal mines, the distribution of stress fields in deep mining becomes more complex, and the stress localization characteristics are obvious. In order to obtain the local mechanical properties and energy evolution of sandstone, this article is based on the three-point bending experiment and combined with the localized failure theory to explore the evolution law of stress field, deformation field, and energy field of sandstone specimen under tensile stress during the three-point bending experiment. The results show that during the three-point bending test of sandstone, with the increase of the span of the three-point bending test, the peak stress at the characteristic point shows an increasing trend, and the peak stress has obvious regional characteristics. In the vertical direction, the peak stress at the characteristic points in the upper part of the neutral layer is larger, and the peak stress at the characteristic points in the lower part of the neutral layer is smaller. In the horizontal direction, the peak stress at the characteristic points in the near field is higher, and the peak stress at the characteristic points in the middle field and the far field is smaller. The stress field and the deformation field have a good corresponding relationship. The upper far-field peak strain tends to decrease with the increase of the span, and the upper near-field peak strain first decreases and then increases with the increase of the span. The lower near-field peak strain tends to decrease and then increase with increasing span, and the lower far-field peak strain fluctuates with increasing span. The energy field is dependent on the stress field and the deformation field, showing obvious regional characteristics. The energy storage and release capacity of the upper area are higher than those of the lower area. The overall performance of the loading energy storage, rebound energy release, and crack propagation energy release in different areas can be described as far field < mid-field << near field. The near-field energy at different spans presents the characteristics of two stages. When the span is between 140 mm and 150 mm, the near-field energy shows a rapid decreasing trend, and when the span is between 150 mm and 180 mm, the near-field energy presents an obvious increasing trend.

Magnetic and resonance properties of the Y0.5Sr0.5Cr0.5Mn0.5O3 polycrystal

The magnetostatic and magnetic resonance properties of the Y0.5Sr0.5Cr0.5Mn0.5O3 polycrystalline system have been experimentally studied. The intracrystalline ferromagnetic interaction turned out to be prevalent while the intercrystalline interaction appears to have antiferromagnetic character. We found that two absorption lines are observed in the spectrum in the magnetic ordering region at T < 80 K. The high-field line corresponds to the interacting parts of polycrystal related to the disordered shells and the low-field peak is system of ferromagnetic particles.

Simulation of Solar Cells with Integration of Optical Nanoantennas

The evolution of nanotechnology has provided a better understanding of light-matter interaction at a subwavelength scale and has led to the development of new devices that can possibly play an important role in future applications. Nanoantennas are an example of such devices, having gained interest in recent years for their application in the field of photovoltaic technology at visible and infrared wavelengths, due to their ability to capture and confine energy of free-propagating waves. This property results from a unique phenomenon called extraordinary optical transmission (EOT) where, due to resonant behavior, light passing through subwavelength apertures in a metal film can be transmitted in greater orders of magnitude than that predicted by classical theories. During this study, 2D and 3D models featuring a metallic nanoantenna array with subwavelength holes coupled to a photovoltaic cell are simulated using a Finite Element Tool. These models present with slight variations between them, such as the position of the nanoantenna within the structure, the holes’ geometry and the type of cell, in order to verify how its optical response is affected. The results demonstrate that the coupling of nanoantennas to solar cells can be advantageous and improve the capture and absorption of radiation. It is concluded that aperture nanoantennas may concentrate radiation, meaning that is possible to tune the electric field peak and adjust absorption on the main layers. This may be important because it might be possible to adjust solar cell performance to the global regions’ solar spectrum by only adjusting the nanoantenna parameters.

An Optimized Structure of Split-Gate Resurf Stepped Oxide UMOSFET

In this paper, a split-gate resurf stepped oxide with double floating electrodes (DFSGRSO) U-shape metal oxide semiconductor field-effect transistor (UMOSFET) is proposed. The floating electrodes are symmetrically distributed on both sides of the source electrode in the trench. The performance of the DFSGRSO UMOSFET with different size of floating electrodes is simulated and analyzed. The simulation results reveal that the floating electrodes can modulate the distribution of the electric field in the drift area, improving the performance of the device significantly. The breakdown voltage (BV) and figure of merit (FOM) of the DFSGRSO UMOSFET at optimal parameters are 23.6% and 53.1% higher than that of the conventional structure. In addition, the regulatory mechanism of the floating electrodes is analyzed. The electric field moves from the bottom of the trench to the middle of the drift area, which brings a new electric field peak. Therefore, the distribution of the electric field is more uniform for the DFSGRSO UMOSFET compared with the conventional structure.

Магнитные и резонансные свойства поликристалла Y-=SUB=-0.5-=/SUB=-Sr-=SUB=-0.5-=/SUB=-Cr-=SUB=-0.5-=/SUB=-Mn-=SUB=-0.5-=/SUB=-O-=SUB=-3-=/SUB=-

The magnetostatic and magnetic resonance properties of the Y_0.5Sr_0.5Cr_0.5Mn_0.5O_3 polycrystalline system have been experimentally investigated. The predominance of the intracrystalline ferromagnetic interaction and the antiferromagnetic character of the intercrystallite interaction have been established. The magnetic resonance spectrum in the magnetically ordered region consists of two lines. The high-field line corresponds to the interacting parts of polycrystal shells and the low-field peak is related to the disordered system of ferromagnetic particles.

Assessment of a coupled approach to determine the stress caused by gun blast loads

This paper aims at assessing a custom numerical procedure built to predict the level of stress in the structural components and equipment in proximity of a cannon-like weapon system when firing. In such a blast scenario, the structures adjacent to a gun may undergo sudden and unwanted damages, since they are commonly subjected to the blast load due to the impingement and propagation of the shock waves expanding from the weapon muzzle. The proposed procedure pertains the coupled use of an in-house developed tool (GUNWave3D) based on the power-law scaling technique and a general-purpose commercial fast dynamic solver to compute the structural response of the loaded components. The in-house tool, in particular, allows one to rapidly calculate the blast parameters over the surfaces of the items of interest in the function of the weapon characteristics and launch conditions, also accounting for the asymmetric shape characterizing the gun blast wave. Taking as reference the numerical free field peak overpressure profiles of a 30 mm gun, whose blast quantities were already validated in a previously published work, the final stage of the assessment was accomplished. Such an estimation consists of the comparison between the structural stresses calculated using the blast loads predicted through the in-house tool and those computed adopting the free spherical air blast of the tri-nitro-toluene model. This operation has the objective to quantify the discrepancy between the computational results of two Lagrangian techniques that can be alternatively adopted in industrial gun blast design procedures and methodologies.

A modeling and performance of the triple field plate HEMT

We present this work by two steps. In the first one, the new structure proposed of the FP-HEMTs device (Field plate High Electron Mobility Transistor) with a T-gate on an 4H-SIC substrate to optimize these electrical performances, multiple field-plates were used with aluminum oxide to split the single electric field peak into several smaller peaks, and as passivation works to reduce scaling leakage current. In the next, we include a modeling of a simulation in the Tcad-Silvaco Software for realizing the study of the influence of negative voltage applied to gate T-shaped in OFF state time and high power with ambient temperature, the performance differences between the 3FP and the SFP devices are discussed in detail.

A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

A new approximate method for lightning-radiated extremely low-frequency (ELF) and very low-frequency (VLF) ground wave propagation over intermediate ranges is presented in this paper. In our approximate method, the original field attenuation function is divided into two factors in frequency domain representing the propagation effect of the ground conductivity and Earth’s curvature, and both of them have clearer formulations and can more easily be calculated rather than solving a complex differential equation related to Airy functions. The comparison results show that our new approximate method can predict the lightning-radiated field peak value over the intermediate range with a satisfactory accuracy within maximum errors of 0.0%, −3.3%, and −8.7% for the earth conductivity of 4 S/m, 0.01 S/m, and 0.001 S/m, respectively. We also find that Earth’s curvature has much more effect on the field propagation at the intermediate ranges than the finite ground conductivity, and the lightning-radiated ELF/VLF electric field peak value (V/m) at the intermediate ranges yields a propagation distance d (km) dependence of d−1.32.