"Power semiconductors" are often used for power control of power converters such as converters and inverters. At present, power semiconductor materials are welcoming materials, these new materials are SiC (silicon carbide) and GaN (gallium nitride), both of which have better physical properties than the current Si (silicon), as the "energy saving trump card" Received great expectations from power companies, auto manufacturers and electronics manufacturers. The replacement of Si into a compound semiconductor such as GaN or SiC can greatly improve product efficiency and downsizing, which is impossible for Si power semiconductor devices (hereinafter referred to as power devices). At present, transistors such as Si diodes, MOSFETs, and IGBTs (Insulated Gate Bipolar Transistors) are used as power components in many fields, such as power supply systems, electric locomotives, hybrid vehicles, production equipment in factories, and power conditioners for photovoltaic power generation systems. White goods, air conditioners, and other white goods, servers, and personal computers. The materials of the power components utilized in these fields may soon be replaced by GaN and SiC. For example, SiC has begun to be used as an inverter device for a motor for a railway vehicle, an air conditioner, and the like. Power loss can be reduced by more than 50% The use of power elements made of GaN and SiC reduces the loss of electrical energy because it reduces losses and switching losses during conduction. For example, the inverter uses diodes and transistors as power components. Only the diode material is changed from Si to SiC. The power loss of the inverter can be reduced by about 15 to 30%. If the transistor material is also replaced by SiC, the power loss can be reduced. Reduce it by more than half. Helps products to be miniaturized When the power loss is reduced and the amount of heat generation is reduced accordingly, the power converter can be miniaturized. The power element fabricated using GaN and SiC has two characteristics that enable the power converter to be miniaturized: high-speed switching operation and high heat resistance. GaN and SiC power components can be switched at multiple speeds of Si power components. The higher the switching frequency, the easier it is to achieve miniaturization of components that constitute a power converter, such as an inductor. In terms of heat resistance, Si power components reach their limits at 200 ° C, while both GaN and SiC power components can operate in higher temperature environments, thus reducing or eliminating the cooling mechanism of the power converter. These advantages stem from the physical properties of GaN and SiC. Compared with Si, both have the characteristics of high breakdown voltage, wide band gap, high thermal conductivity, high electron saturation rate and high carrier mobility. SiC diodes are the first to be put into practical use Among GaN and SiC power devices, SiC is the first to be commercialized. In particular, the use of SiC diodes seems to increase rapidly in the future. In addition to the German Infineon Technologies, which originally realized the commercialization of SiC diodes in 2001, companies such as STMicroelectronics and STMicroelectronics have also launched products. In Japan, Roma, Nippon Wireless and Renesas Electronics have produced SiC diodes. Many companies are developing Schottky barrier diodes (SBD), and some companies such as Cree have also introduced "JBS (juncTIon barrier schottky) structure" diodes that combine Schottky junctions and pn junctions. Substrate supply and demand situation improved The increase in the number of companies engaged in SiC diodes is due to the improvement in the supply of SiC substrates that are indispensable for the fabrication of power components. For example, the reduction in crystal defects leads to an increase in the quality of the SiC substrate, and the large diameter of the substrate has also progressed. Products with a 4-inch diameter are gradually becoming mainstream. Samples will be available for 6-inch products in 2012, and it is expected to begin mass production in 2013. In addition, the increase in substrate manufacturers has led to price competition, and the substrate is cheaper than before. The increase in the number of manufacturers engaged in epitaxial substrates (stacked epitaxial layers) has also lowered the barriers to entry into the SiC diode business. In addition to the improved supply of SiC substrates, power Si diodes "have less room for performance improvement than Si transistors" (technically skilled in power components), which has prompted users to use SiC diodes. It has been suggested that although the Si diode is simple in construction, the corresponding improvement in performance is approaching the limit, and the trend of replacing Si with SiC may increase in the future (the above-mentioned technician). The popularity of SiC MOSFETs will begin with channel products Although SiC transistors for power components have been put into production, they are not as popular as diodes and remain in a very small number of special applications. This is because the manufacturing process of the SiC transistor is more complicated than the diode, and the yield is low, so the price is high. And, although the speed is slowing, the performance of Si transistors has been increasing. Compared with diodes, "there is still a lot of room for development" (technician). That is to say, low-cost high-performance Si transistors can be conveniently used at present. Therefore, such research and development is accelerating while continuously reducing the cost of SiC transistors and utilizing the excellent material properties of SiC to pursue performance that Si cannot achieve. SiC transistors are mainly MOSFET, JFET and BJT. Among them, the first to be put into production is JFET. Although the JFET can reduce the power loss, it is basically in the "Normally On" state (on state), and will work even if the gate voltage is not applied. Under normal circumstances, on a high-power power supply circuit, it is desirable to realize a "normally open state" that will not be driven without loading the gate voltage. JFETs also have products that can be used for normally open work. However, MOSFETs are easy to implement in normal operation, so many companies are working on MOSFETs. Cree and Rom have already started producing MOSFETs. But it is not said to be widely popular. The reason is that in addition to the high price, the excellent material properties of SiC have not been fully utilized. Among them, the loss at the time of conduction is large, and the research and development for reducing the on-resistance to reduce the conduction loss are underway. The way to reduce the on-resistance is to dig the channel directly below the gate. The SiC MOSFETs that have been put into production are all "flat". In the planar type, when the cell is miniaturized in order to reduce the channel resistance, the JFET resistance increases, and the decrease in the on-resistance has limitations. The channel type is structurally free of JFET resistors. Therefore, it is suitable for reducing the channel resistance and reducing the on-resistance. Although the channel type can reduce the on-resistance, the mass production is difficult to planar because the channel is to be dug directly below the gate. So it has not yet been put into production. It is estimated that the products of Roma and other products will be available in 2013. GaN-based power components can reduce costs by using silicon substrates GaN has been commercialized in the use of light-emitting elements such as LEDs and semiconductor lasers and high-frequency components for base stations, and the commercialization of power component applications has just begun, falling behind SiC. But this situation is also changing. That is the reduction in manufacturing costs and the rapid increase in electrical characteristics. The reason why GaN-based power components can reduce the cost is because a silicon substrate having a low price and a large aperture can be used. With a silicon substrate, you can use a large diameter product of 6 inches or more. For example, the US EPC company and the US IR use silicon substrates to introduce GaN-based power components by forming epitaxial layers. Improvements have also been made to suppress the "current collapse" phenomenon in which the on-resistance is increased during operation, and to improve electrical characteristics such as withstand voltage. Taking the withstand voltage as an example, although the product is generally lower than 200V, there are more than 1kV research and development products. At present, there are still very few companies that produce GaN-based power components, but it is expected to gradually increase from 2012. Moreover, around 2015, GaN substrates with a reduction in crystal defects to a level that can be used for power components and up to 6 inches in diameter are likely to be available. If a GaN-based power device is formed on a GaN substrate, it is easier to improve electrical characteristics than a power device using a different material such as a silicon substrate. Interactive Smart Board,Smart Boards,Smart Board Projector,Smart Electric Board ALLIN , https://www.nbdisplayapio.com