scholarly journals EFFECT OF AlN LAYERS ON THE AlxGa1-xN/GaN GROWN ON SAPPHIRE SUBSTRATES

2019 ◽  
Author(s):  
Kheam Bun
Keyword(s):  
Surface Roughness ◽  
Sapphire Substrate ◽  
Electronic Devices ◽  
Lower Surface ◽  
Experimental Results ◽  
Power Electronic ◽  
Electrical Characteristics ◽  
Sapphire Substrates ◽  
Gan Heterostructure

The effect of a thin AlN layer inserted between AlxGa1-xN/GaN heterostructures grown on sapphire substrates was investigated for possible application in opto-electronic and power electronic devices. The heterostructures with two different Al compositions (0.35 and 0.49) were applied to study. After growing a thin AlN interlayer (~10nm) on the buffer GaN/AlN/sapphire substrate, then a thick AlxGa1-xN/GaN heterostructure were grown and investigated the Al mole fractions. Low rocking curves were also achieved with 0.35 and 0.48 for the 0.3 and 0.49 Al compositions, respectively. The experimental results show that with an increasing of Al composition, the crystallinity is also improved with lower surface roughness. The AlxGa1-xN/GaN heterostructures with 0.35 and 0.49 Al compositions were also investigated the electrical characteristics to confirm that they are suitable for development in optoelectronic and power electronic devices.

Grinding Performance Evaluation of the Developed Chemo-Mechanical Grinding (CMG) Tools for Sapphire Substrate

2012 ◽  
Vol 565 ◽  
pp. 105-110 ◽  
Author(s):  
Zhi Gang Dong ◽  
Shang Gao ◽  
P. Zhou ◽  
Ren Ke Kang ◽  
Dong Ming Guo
Keyword(s):  
Surface Roughness ◽  
Performance Evaluation ◽  
Surface Quality ◽  
Sapphire Substrate ◽  
Physicochemical Characteristics ◽  
Diamond Wheel ◽  
Mechanical Grinding ◽  
Sapphire Substrates ◽  
Grinding Performance

In order to improve the surface quality of sapphire substrates ground by diamond wheel, the chemo-mechanical grinding (CMG) tools for sapphire grinding was investigated in this paper. According to the processing principle of CMG, three CMG tools with different abrasives of SiO2, Fe2O3 and MgO were developed respectively. The compositions of the CMG tools were designed and optimized based on the physicochemical characteristics of sapphire. The grinding experiments were performed with the developed CMG tools and the grinding performance of three kind of tools were evaluated by comparing the surface roughness and the MRR of sapphire. The experiment results show that the grinding performance of SiO2 CMG tool was worst. The surface roughness and MRR corresponding to SiO2 CMG tool were all significantly poorer than Fe2O3 and MgO CMG tools. The highest MRR could be obtained by Fe2O3 CMG tool, but the best surface quality was obtained by MgO CMG tool.

scholarly journals Contrast Experiments in Dielectrophoresis Polishing (DEPP)/Chemical Mechanical Polishing (CMP) of Sapphire Substrate

2019 ◽  
Vol 9 (18) ◽  
pp. 3704 ◽  
Author(s):  
Tianchen Zhao ◽  
Julong Yuan ◽  
Qianfa Deng ◽  
Kaiping Feng ◽  
Zhaozhong Zhou ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Sapphire Substrate ◽  
Chemical Mechanical Polishing ◽  
Mechanical Polishing ◽  
Uniform Electric Field ◽  
Maximum Increase ◽  
Sapphire Surface ◽  
Sapphire Substrates ◽  
Better Than ◽  
Surface Changes

The broad applications of sapphire substrates in many fields warrants an urgent demand for a highly efficient and high precision polishing method for the sapphire substrates. The authors proposed a novel sapphire substrate polishing method that is based on the dielectrophoresis (DEP) effect. The principle of dielectrophoresis polishing (DEPP) is described. A non-uniform electric field was added in the polishing area to drive abrasives moving in the direction towards the plate by the DEP force. The amount of abrasives that participates in the polishing action increases as the distribution of polishing slurry on sapphire surface changes, leading towards the improvement of sapphire polishing both in quality and efficiency. Comparative experiments between DEPP and traditional chemical mechanical polishing (CMP) were carried out. It was found that the maximum increase of sapphire MRR for DEPP is 71%, reaching 13 mg/h, and the minimum increase was 9.5%, reaching 4.6 mg/h. The surface roughness of the sapphire substrate decreases faster and more uniform with DEPP. The final surface roughness of the sapphire substrate after DEPP was Ra 0.87 nm and the flatness was 0.3078 waves (RMS value), which is better than 0.6863 waves (RMS value) of sapphire substrate with traditional CMP polishing.

New Extendable 15-Level Basic Unit for Multilevel Inverters

2016 ◽  
Vol 25 (12) ◽  
pp. 1650151 ◽  
Author(s):  
Ebrahim Babaei ◽  
Sara Laali
Keyword(s):  
Electronic Devices ◽  
Lower Number ◽  
Multilevel Inverter ◽  
Experimental Results ◽  
Installation Space ◽  
Basic Unit ◽  
Power Electronic ◽  
Total Cost ◽  
Dc Voltage ◽  
Multilevel Inverters

In this paper, a new basic 15-level inverter is proposed. By developing the proposed basic unit, a 71-level inverter and generally an [Formula: see text]-level inverter are proposed. Then, the proposed multilevel inverter is compared with several conventional multilevel inverters in design of minimum 15 levels and 71 levels at the output. By comparing these inverters, it is obtained that the proposed inverter is able to generate higher number of output levels by using lower number of DC voltage sources and power electronic devices that lead to decreased complexity, installation space and total cost of the inverter. Finally, the correct performance of the proposed inverter is reconfirmed through the simulation and experimental results of a 15-level inverter.

Research on Surface Roughness of Ultrasonic Polishing without Abrasive Based on Orthogonal Experiments

2009 ◽  
Vol 416 ◽  
pp. 133-136
Author(s):  
Jian Jun Jiang ◽  
Jian Xin Zheng ◽  
Chuan Shao Liu
Keyword(s):  
Surface Roughness ◽  
Feed Rate ◽  
Lower Surface ◽  
Orthogonal Test ◽  
Test Method ◽  
Experimental Results ◽  
Polished Surface ◽  
Orthogonal Experiments ◽  
Orthogonal Test Method ◽  
Conventional Rolling

Experiments of ultrasonic polishing the 45# steel shaft without abrasive are carried out by using orthogonal test method to study the polished surface roughness, and experimental results are analyzed with range method. The influence of polishing parameters on the polished surface roughness could be arranged as follows: feed rate, power of generator, preload pressure and radius of the tool head, in which the feed rate brings the most remarkable influence on the polished surface roughness. The surface roughness value reduces at first and then increases when the radius of tool head, preload pressure and power of the generator increase. The surface roughness value increases with the feed rate. Comparative experimental results of ultrasonic polishing without abrasive and the conventional rolling indicate that lower surface roughness value may be obtained by ultrasonic polishing without abrasive.

Influence of Si Surface Roughness on Electrical Characteristics of MOSFET with HfON Gate Insulator Formed by ECR Plasma Sputtering

2014 ◽  
Vol E97.C (5) ◽  
pp. 413-418 ◽  
Author(s):  
Dae-Hee HAN ◽  
Shun-ichiro OHMI ◽  
Tomoyuki SUWA ◽  
Philippe GAUBERT ◽  
Tadahiro OHMI
Keyword(s):  
Surface Roughness ◽  
Gate Insulator ◽  
Electrical Characteristics ◽  
Ecr Plasma ◽  
Plasma Sputtering

scholarly journals Research on Small Square PCB Rogowski Coil Measuring Transient Current in the Power Electronics Devices

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4176 ◽  
Author(s):  
Chaoqun Jiao ◽  
Juan Zhang ◽  
Zhibin Zhao ◽  
Zuoming Zhang ◽  
Yuanliang Fan
Keyword(s):  
Power Electronics ◽  
Printed Circuit Board ◽  
Electronic Devices ◽  
Rogowski Coil ◽  
Bipolar Transistors ◽  
Circuit Board ◽  
Power Electronic ◽  
Insulated Gate Bipolar Transistors ◽  
Printed Circuit ◽  
Internal Structures

With the development of China’s electric power, power electronics devices such as insulated-gate bipolar transistors (IGBTs) have been widely used in the field of high voltages and large currents. However, the currents in these power electronic devices are transient. For example, the uneven currents and internal chip currents overshoot, which may occur when turning on and off, and could have a great impact on the device. In order to study the reliability of these power electronics devices, this paper proposes a miniature printed circuit board (PCB) Rogowski coil that measures the current of these power electronics devices without changing their internal structures, which provides a reference for the subsequent reliability of their designs.

scholarly journals New Sensor for Medium- and High-Voltage Measurement

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4654
Author(s):  
Andrzej Wetula ◽  
Andrzej Bień ◽  
Mrunal Parekh
Keyword(s):  
Finite Element Method ◽  
Electronic Devices ◽  
Finite Element Method Simulation ◽  
Laboratory Model ◽  
Power Electronic ◽  
Proof Of Concept ◽  
Voltage Measurement ◽  
Medium Voltage ◽  
Narrow Frequency Band ◽  
Further Development

Measurements of medium and high voltages in a power grid are normally performed with large and bulky voltage transformers or capacitive dividers. Besides installation problems, these devices operate in a relatively narrow frequency band, which limits their usability in modern systems that are saturated with power electronic devices. A sensor that can be installed directly on a wire and can operate without a galvanic connection to the ground may be used as an alternative voltage measurement device. This type of voltage sensor can complement current sensors installed on a wire, forming a complete power acquisition system. This paper presents such a sensor. Our sensor is built using two dielectric elements with different permeability coefficients. A finite element method simulation is used to estimate the parameters of a constructed sensor. Besides simulations, a laboratory model of a sensor was built and tested in a medium-voltage substation. Our results provide a proof of concept for the presented sensor. Some errors in voltage reconstruction have been traced to an oversimplified data acquisition and transmission system, which has to be improved during the further development of the sensor.

scholarly journals Series Compensation of Transmission Systems: A Literature Survey

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1717
Author(s):  
Camilo Andrés Ordóñez ◽  
Antonio Gómez-Expósito ◽  
José María Maza-Ortega
Keyword(s):  
Steady State ◽  
Power Systems ◽  
Power System ◽  
Case Studies ◽  
Electronic Devices ◽  
Literature Survey ◽  
Power Electronic ◽  
Transmission Systems ◽  
Series Compensation ◽  
Near Future

This paper reviews the basics of series compensation in transmission systems through a literature survey. The benefits that this technology brings to enhance the steady state and dynamic operation of power systems are analyzed. The review outlines the evolution of the series compensation technologies, from mechanically operated switches to line- and self-commutated power electronic devices, covering control issues, different applications, practical realizations, and case studies. Finally, the paper closes with the major challenges that this technology will face in the near future to achieve a fully decarbonized power system.

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