Search Results (19)

Edge termination techniques play a crucial role in enhancing the breakdown voltage (BV) and managing electric field distribution in GaN-based power devices. This review explores six key termination methods—field plate (FP), mesa, bevel, trench, ion implantation, and guard ring (GR)—with a focus on their performance, fabrication complexity, and insights derived from TCAD simulations. FP and trench terminations excel in high-voltage applications due to their superior electric field control but are accompanied by significant fabrication challenges. Mesa and bevel terminations, while simpler and cost-effective, are more suited for medium-voltage applications. Ion implantation and GR techniques strike a balance, offering customizable parameters for improved BV performance. TCAD simulations provide a robust framework for analyzing these techniques, highlighting optimal configurations and performance trade-offs. The choice of edge termination depends on the specific application, balancing BV requirements with manufacturing feasibility. This review offers a comprehensive comparison, emphasizing the critical role of simulations in guiding the selection and design of edge termination techniques for GaN power devices. Full article

The study of velocimetry is important for characterizing and comprehending the effects of fluid flow, and the particle image velocimetry (PIV) technique is one of the primary approaches for understanding the velocity vector field in a test section. Commercial PIV systems are expensive, with one of the main cost factors being high-speed camera equipment capable of capturing images at high frames per second (fps), rendering them impractical for many applications. This study proposes an evaluation of utilizing smartphones as accessible image acquisition systems for PIV technique application. An experimental setup inspired by the known angular displacement of synthetic particles is proposed. A stepper motor rotates a plate containing an image of synthetic particles on its surface. The motion of the plate is captured by the smartphone camera, and the images are processed using PIVlab-MatLab^® software. The use of two smartphones is assessed, with acquisition rates of either 240 fps or 960 fps and varying angular velocities. The results were satisfactory for velocities up to 0.7 m/s at an acquisition rate of 240 fps and up to 1.8 m/s at 960 fps, validating the use of smartphones as a cost-effective alternative for applying the PIV technique, both for educational purposes and for research carried out in low-income organizations. Full article

In this work, by employing field plate (FP) and N ion-implantation edge termination (NIET) structure, the electrical performance of the β-Ga₂O₃ Schottky barrier diode (SBD) was greatly improved. Ten samples of vertical SBDs were fabricated to investigate the influence of the relative positions of field plates (FPs) and ion implantation on the device performance. The device with the FP of 15 μm and the ion implantation at the edge of the Schottky electrode exhibited a breakdown voltage (V_br) of 1616 V, a specific on-resistance (R_on,sp) of 5.11 mΩ·cm², a power figure of merit (PFOM) of 0.511 GW/cm², and a reverse current density of 1.2 × 10⁻⁵ A/cm² @ −1000 V. Compared to the control device, although the R_on,sp increased by 1 mΩ·cm², the V_br of the device increased by 183% and the PFOM increased by 546.8%. Moreover, the reverse leakage current of the device with the FP and NIET structure decreased by three orders of magnitude. The TCAD simulation revealed that the peak electric field at the interface decreased from 7 MV/cm @ −500 V to 4.18 MV/cm @ −1000 V. These results demonstrate the great potential for the β-Ga₂O₃ SBD with a FP and NIET structure in power electronic applications. Full article

This paper proposes a concept based on field plate (FP) integration inside printed circuit board (PCB)-embedded power modules. The goal is to reduce the electric field at their surface and thus increase the partial discharge inception voltage (PDIV). Electrostatic simulations are first carried out to analyze the electric field reduction induced by the use of FPs. Then, dedicated experiments are proposed to demonstrate that the actual PDIV increases in AC sinus 50 Hz when FPs are implemented. More specifically, it is observed that an optimal FP length exists. Several analyses based on simulations and experiments are thus proposed to explain this phenomenon. Finally, an assessment of PD activity and PD location is presented to support the analysis. AC sinus 50 Hz characterizations indicate that PDIV can be increased by 178% compared to PCBs without FPs with a proper definition of equipotential prolongation and PCB length. Full article

In this study, we developed an analytic model to design a trench metal–insulator–semiconductor (MIS) field plate (FP) structure for the edge termination of a vertical GaN PN diode. The key parameters considered in the trench MIS FP structure include trench depth, MIS dielectric material and thickness, and interface charge density of MIS. The boundary conditions are defined based on the maximum allowed electric field strengths at the dielectric and semiconductor regions. The developed model was validated using TCAD simulations. As an example, a 1 kV GaN vertical PN diode was designed using the optimized FP structure, which exhibited the same breakdown voltage characteristics as an ideal one-dimensional PN diode structure without edge effects. This proposed simple analytic model offers a design guideline for the trench MIS FP for the edge termination of vertical PN diodes, enabling efficient design without the need for extensive TCAD simulations, thus saving significant time and effort. Full article

In this paper, DC, transient, and RF performances among AlGaN/GaN HEMTs with a no field plate structure (basic), a conventional gate field plate structure (GFP), and a double floating field plate structure (2FFP) were studied by utilizing SILVACO ATLAS 2D device technology computer-aided design (TCAD). The peak electric fields under the gate in drain-side can be alleviated effectively in 2FFP devices, compared with basic and GFP devices, which promotes the breakdown voltage (BV) and suppresses the current collapse phenomenon. As a result, the ON-resistance increase caused by the current collapse phenomena is dramatically suppressed in 2FFP ~19.9% compared with GFP ~49.8% when a 1 ms duration pre-stress was applied with V_ds = 300 V in the OFF-state. Because of the discontinuous FP structure, more electric field peaks appear at the edge of the FFP stacks, which leads to a higher BV of ~454.4 V compared to the GFP ~394.3 V and the basic devices ~57.6 V. Moreover, the 2FFP structure performs lower a parasitic capacitance of C_gs = 1.03 pF and C_gd = 0.13 pF than those of the GFP structure (i.e., C_gs = 1.89 pF and C_gd = 0.18 pF). Lower parasitic capacitances lead to a much higher cut-off frequency (f_t) of 46 GHz and a maximum oscillation frequency (f_max) of 130 GHz than those of the GFP structure (i.e., f_t = 27 GHz and f_max = 93 GHz). These results illustrate the superiority of the 2FFP structure for RF GaN HEMT and open up enormous opportunities for integrated RF GaN devices. Full article

In the field of intelligent robot and automatic drive, the task of license plate detection and recognition (LPDR) are undertaken by mobile edge computing (MEC) chips instead of large graphics processing unit (GPU) servers. For this kind of small computing capacity MEC chip, a light LPDR network with good performance in accuracy and speed is urgently needed. Contemporary deep learning (DL) LP recognition methods use two-step (i.e., detection network and recognition network) or three-step (i.e., detection network, character segmentation method, and recognition network) strategies, which will result in loading two networks on the MEC chip and inserting many complex steps. To overcome this problem, this study presents an end-to-end light LPDR network. Firstly, this network adopts the light VGG16 structure to reduce the number of feature maps and adds channel attention at the third, fifth, and eighth layers. It can reduce the number of model parameters without losing the accuracy of prediction. Secondly, the prediction of the LP rotated angle is added, which can improve the matching between the bounding box and the LP. Thirdly, the LP part of the feature map is cropped by the relative position of detection module, and the region-of-interest (ROI) pooling and fusion are performed. Seven classifiers are then used to identify the LP characters through the third step’s fusion feature. At last, experiments show that the accuracy of the proposed network reaches 91.5 and that the speed reaches 63 fps. In the HiSilicon 3516DV300 and the Rockchip Rv1126 Mobile edge computing chips, the speed of the network has been tested for 15 fps. Full article

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by applying a slant-gate structure and drain-side extended field-plate (FP) for improved breakdown voltage. Prior to the analysis of slant-gate-based HEMT, simulation parameters were extracted from the measured data of fabricated basic T-gate HEMTs to secure the reliability of the results. We suggest three different types of slant-gate structures that connect the basic T-gate electrode boundary to the 1st and 2nd SiN passivation layers obliquely. To consider both the breakdown voltage and frequency characteristics, the DC and RF characteristics of various slant-gate structures including the self-heating effect were analyzed by TCAD simulation. We then applied a drain-side extended FP to further increase the breakdown voltage. The maximum breakdown voltage was achieved at the FP length of 0.4 μm. Finally, we conclude that the slant-gate structures can improve breakdown voltage by up to 66% without compromising the frequency characteristics of the HEMT. When the drain-side FP is applied to a slant-gate structure, the breakdown voltage is further improved by up to 108%, but the frequency characteristics deteriorate. Therefore, AlGaN/GaN HEMTs with an optimized slant-gate-based structure can ultimately be a promising candidate for high-power and high-frequency applications. Full article

This study optimized the field plate (FP) design (i.e., the number and positions of FP layers) of p-GaN power high-electron-mobility transistors (HEMTs) on the basic of simulations conducted using the technology computer-aided design software of Silvaco. Devices with zero, two, and three FP layers were designed. The FP layers of the HEMTs dispersed the electric field between the gate and drain regions. The device with two FP layers exhibited a high off-state breakdown voltage of 1549 V because of the long distance between its first FP layer and the channel. The devices were subjected to high-temperature reverse bias and high-temperature gate bias measurements to examine their characteristics, which satisfied the reliability specifications of JEDEC. Full article

AlGaN/GaN HEMTs with several different designs of field plate structure are studied for device optimization purposes. To increase device breakdown voltage, optimal dimensions of field plates were first investigated using Silvaco TCAD software, and the electrical characteristics of the devices are analyzed. Several devices were designed and fabricated based on the simulation results. It has been confirmed that the gate-source composite field plate (SG-FP) has a higher breakdown voltage than other types of field plate structures, with FOM reaches 504 MW/cm⁻², showing that the device with SG-FP structure outperforms the other three structures. The experiment and simulation verify that the gate-source composite field plate optimizes FOM by increasing the breakdown voltage and reducing the intrinsic on-resistance so that the device has better electrical performance and a wider application range. Full article

In this paper, we introduce a new type of AlGaN/GaN high electron mobility transistor (HEMT) with microfield plate (FP). We use Silvaco-ATLAS two-dimensional numerical simulation to calculate the performance of conventional HEMT and HEMT with micro-FP and analyze its principle. By studying a new charge balance method provided by HEMTs and micro-FPs, the physical mechanism of FP adjusting the HEMT potential distribution and channel electric field distribution is analyzed. The new FP structure consists of a drain field plate (D-FP), a source field plate (S-FP) and several micro-gate field plates (G-FP) to improve the output characteristics of HEMTs. By adjusting the distribution of potential and channel electric field, a wider and more uniform channel electric field can be obtained, and the breakdown voltage can be increased to 1278 V. Although the on-resistance of the HEMT is slightly increased to 5.24 $\Omega$ mm, it is still lower than other reference values. These results may open up a new and effective method for manufacturing high-power devices for power electronics applications. Full article

The geochemistry on Holocene lavas from the Jingpohu volcanic field in NE China are compared with other Cenozoic lavas from across the back-arc rift of NE China, in order to constrain their enriched mantle sources. Holocene lavas within Jingpohu volcanic field comprise two separate “Crater Forest” (CF) and “Frog Pool” (FP) volcanic areas. FP lavas have lower MgO, CaO, and heavy rare earth elements and higher Al₂O₃, Na₂O, K₂O, and large-ion lithophile elements than CF lavas. Yet, both CF and FP lavas share similar isotopic signatures, with depleted Sr and Nd isotopes (⁸⁷Sr/⁸⁶Sr = 0.703915–0.704556, ¹⁴³Nd/¹⁴⁴Nd = 0.512656–0.512849) and unradiogenic Pb isotopes (²⁰⁸Pb/²⁰⁴Pb = 37.79–38.06, ²⁰⁷Pb/²⁰⁴Pb = 15.45–15.54, ²⁰⁶Pb/²⁰⁴Pb = 17.49–18.15), similar to oceanic island basalts. An important new constraint for the Jingpohu lavas lies in their Ca isotopes of δ^44/40Ca from 0.63‰ to 0.77‰, which are lower than that of the bulk silicate earth (0.94 ± 0.05‰). By comparing the isotopic signatures of sodic lavas with that of the potassic lavas across NE China, we propose a three-component mixing model as the source for the sodic lavas. In consistence with geophysical results, we propose that subducting Pacific plate induces asthenospheric mantle upwelling of an upper depleted mantle (DM), including subducted ancient sediments (EM I), which partially melted upon ascent. These primary melts further interacted with the lithospheric mantle (EM II), before differentiating within crustal magma chambers and erupting. Full article

Fatigue increases the risk of injury during sports training and rehabilitation. Early detection of fatigue during exercises would help adapt the training in order to prevent over-training and injury. This study lays the foundation for a data-driven model to automatically predict the onset of fatigue and quantify consequent fatigue changes using a force plate (FP) or inertial measurement units (IMUs). The force plate and body-worn IMUs were used to capture movements associated with exercises (squats, high knee jacks, and corkscrew toe-touch) to estimate participant-specific fatigue levels in a continuous fashion using random forest (RF) regression and convolutional neural network (CNN) based regression models. Analysis of unseen data showed high correlation (up to 89%, 93%, and 94% for the squat, jack, and corkscrew exercises, respectively) between the predicted fatigue levels and self-reported fatigue levels. Predictions using force plate data achieved similar performance as those with IMU data; the best results in both cases were achieved with a convolutional neural network. The displacement of the center of pressure (COP) was found to be correlated with fatigue compared to other commonly used features of the force plate. Bland–Altman analysis also confirmed that the predicted fatigue levels were close to the true values. These results contribute to the field of human motion recognition by proposing a deep neural network model that can detect fairly small changes of motion data in a continuous process and quantify the movement. Based on the successful findings with three different exercises, the general nature of the methodology is potentially applicable to a variety of other forms of exercises, thereby contributing to the future adaptation of exercise programs and prevention of over-training and injury as a result of excessive fatigue. Full article

The aerodynamic and thermal behaviour of multiperforated zones in combustors is essential to the development of future combustion chambers. Detailed databases are therefore crucial for the validation of RANS/LES solvers, but also regarding the derivation of heat transfer correlations used in 0D/1D in-house codes developed by engine manufacturers. In the framework of FP7 EU SOPRANO Program, the test-rig used in a previous study is modified to be compatible with anisothermal conditions. The plate studied is a 12:1 model with a ${90}^{\circ }$ compound angle injection. A heating system is used to generate a moderate temperature gradient of about 20 K between the secondary hot flow and the main cold flow. The aerodynamic field is acquired by a PIV 2D-3C (Stereo Particle Image Velocimetry) system. The surface heat transfer coefficient is derived based on surface temperature distribution acquisitions. Several heating power levels are tested, which allows evaluating the convective heat transfer coefficient and reference temperature through a linear regression. Measurements are conducted on both sides of the plate, which also gives access to those quantities on the injection/suction sides. From a numerical point of view, the configuration is studied using the unstructured ONERA in-house CEDRE solver with an advanced Reynolds Stress Model. A systematic comparison is presented between the experimental and numerical database. Due to the high blowing ratio, the film protection is low in the first rows, with a convective heat transfer coefficient enhancement around three, and freestream cold air brought close to the wall by vortices created at injection. After four rows, the film is building up, leading gradually to a better insulation of the wall. The comparison with the numerical simulation exhibits a qualitative agreement on the main flow structures. However, the mixing between the jets, the film and the freestream is underestimated by the calculation. Full article

In this study, a novel low impact ionization rate (low-IIR) poly-Si thin film transistor featuring a current and electric field split (CES) structure with bottom field plate (BFP) and partial thicker channel raised source/drain (RSD) designs is proposed and demonstrated. The bottom field plate design can allure the electron and alter the electron current path to evade the high electric field area and therefore reduce the device IIR and suppress the kink effect. A two-dimensional device simulator was applied to describe and compare the current path, electric field magnitude distributions, and IIR of the proposed structure and conventional devices. In addition, the advantages of a partial thicker channel RSD design are present, and the leakage current of CES-thin-film transistor (TFT) can be reduced and the ON/OFF current ratio be improved, owing to a smaller drain electric field. Full article