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We developed V-groove trench gate SiC MOSFETs with grounded buried p+ regions. An effective reduction in the feedback capacitance (Crss) and a fast switching performance are achieved. The grounded buried p+ regions are found to be an effective structure for reducing a switching loss.
A critical issue with the SiC UMOSFET is the need to develop a shielding structure for the gate oxide at the trench bottom without any increase in the JFET resistance. This study describes our new UMOSFET named IE-UMOSFET, which we developed to cope with this trade-off. A simulation showed that a low on-resistance is accompanied by an extremely low gate oxide field even with a negative gate voltage...
In order to achieve a high-quality SiC crystal in solution growth, one of the most difficult issues is to grow a thick layer on Si face avoiding polytype transformation. In this case, two-dimensional nucleation, which leads to the polytype transformation, is frequently induced because a density of threading screw dislocations acting as a source of spiral step decreases and wide terraces form by step...
The relationship between surface morphology and spatial distribution of basal plane dislocations in 4H-SiC crystal grown by top-seeded solution growth on the C face was investigated by the differential interference microscopy as well as X-ray topography. Basal plane dislocations were generated at the boundaries of the domains with the different macrosteps advance directions. On the other hand, at...
A novel method for constructing an integrated gradiometer and magnetometer is proposed based on Fundamental mode Orthogonal Fluxgate (FM-OFG) operation [1]. The new method is an extension from the recently presented FM-OFG gradiometer (3 mm diameter, 30 mm length) where the signal subtraction is made at the sensor head level [2], in which the capability of suppressing the response to uniform magnetic...
In high-power density power converter designs, power losses of power devices are essential design parameters because they determines the volume of cooling systems. The power loss of a SiC power module using a SiC Implantation and Epitaxial MOSFET (SiC-IEMOSFET) has been evaluated in the junction temperature range from 150°C to 250°C and the current density range from 100 A/cm2 to 250 A/cm2. By using...
Video streaming with HDTV or UHDV quality will be provided and widely demanded in the future. However, the transmission bit-rate of high-quality video streaming is quite large, so generated traffic flows will cause link congestion. Therefore, when providing streaming services of rich content, it is important to flatten the link utilization, i.e., reduce the maximum link utilization. To achieve this...
In high-power density power converter designs, power losses of power devices are essential design parameters. Silicon-carbide (SiC) power devices are expected as next generation power devices due to their superior performances compared to conventional silicon (Si) power devices. The power loss performances of a SiC power module using SiC Implantation and Epitaxial MOSFET (SiC-IEMOSFET) and Junction...
As a promising solution to manage the huge workload of large-scale VoD services, managed peer-assisted CDN systems, such as P4P has attracted attention. Although the approach works well in theory or in a controlled environment, to our best knowledge, there have been no general studies that address how actual peers can be incentivized in the wild Internet; thus, deployablity of the system with respect...
We describe a method of adaptively controlling bandwidth allocation to flows for reducing the file transfer time of short flows without decreasing throughput of long-duration large flows. According to the rapid increase in Internet traffic volume, effective traffic engineering is increasingly required. Specifically, the traffic of long-duration large flows due to the use of peer-to-peer applications,...
The transmission bandwidth consumed by delivering rich content, such as movie files, is enormous, so it is urgent for ISPs to design an efficient delivery system minimizing the amount of network resources consumed. To efficiently deliver web content, a content delivery networks (CDNs) have been widely used. CDN providers collocate a huge number of servers within multiple ISPs without being informed...
A three-point finite-difference formula is derived for the analysis of a step-index waveguide with a tilted interface. The formula is suitable for the use of the alternating-direction implicit method. Through the analysis of a rib waveguide with a sloped side wall and a hollow triangular waveguide, improvement in accuracy and stability is demonstrated.
We propose a method of identifying anomalous traffic sources using flow statistics. We have investigated a way of detecting whether or not anomalies occur by observing the behavior of several time-series of flow statistics such as the number of flows. After detecting the occurrences of network anomalies, we need to identify the source of the anomalies. In this paper, we describe a method of identifying...
We present a method of detecting network anomalies, such as DDoS (distributed denial of service) attacks and flash crowds, automatically in real time. We evaluated this method using measured traffic data and found that it successfully differentiated suspicious traffic. In this paper, we focus on cyclic traffic, which has a daily and/or weekly cycle, and show that the differentiation accuracy is improved...
In the Internet, the rapid spread of worms is a serious problem. In many cases, worm-infected hosts generate a huge amount of flows with small size to search for other target hosts by scanning. Therefore, we defined hosts generating many flows, i.e., more than or equal to the threshold during a measurement period, as superspreaders, and we proposed a method of identifying superspreaders by flow sampling...
We propose an efficient channel control scheme for gathering data from many observation points scattered over an ultra-wide area using a satellite communication system. There are a huge number of observation points, and the data packets to be transmitted are relatively short. To implement the system economically, the proposed scheme is expected to manage tons of channels correctly without large control...
Power losses of 700V 2.7mOmegacm2 SiC-MOSFETs including influences of circuit stray inductances have been investigated with an originally developed circuit power loss simulator. The device parameters of the SiC-MOSFETs for the power loss calculation are extracted from a SiC-IEMOSFET fabricated at AIST PERC. The power losses of three types of chip areas are investigated and compared to power loss of...
This paper intends to specifically verify what patent issues may be encountered in the telemedicine. Where "telemedicine" is defined as " the use of electronic information and communication technologies to provide and support health care when distance separates the participants", the technologies are concerned, when discussing the "telemedicine", and we cannot avoid thinking...
Normally-off power MOSFET with low Rons has been developed. IEMOSFET on 4H-SiC carbon-face wafer exhibits an extremely low Rons of 1.8 mOmegacm2 with a blocking voltage of 660 V. The effective channel mobility of this device is 90 cm2/Vs which corresponds to the channel resistance of 0.8 mOmegacm2. A step-down converter was fabricated with the normally-off IEMOSFET and SBD, and the operation of 400...
The power MOSFET on 4H-SiC is an attractive high-speed and low-dissipation power switching device. The problem to be solved before realizing the 4H-SiC power MOSFET with low on-resistance is low channel mobility at the SiO2/SiC interface. This work has succeeded in increasing the channel mobility in the buried channel IEMOSFET on carbon-face substrate, and has achieved an extremely low on-resistance...
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