What is Silicon Carbide (SiC)?
Silicon carbide belongs to the third generation of semiconductor materials, compared with ordinary silicon materials, silicon carbide advantages are very prominent, it not only overcomes some of the shortcomings of ordinary silicon materials, power consumption is also a very good performance, and thus become the most promising semiconductor materials in the field of power electronics at present. Because of this, more and more semiconductor companies have begun to enter the SiC market.
Silicon carbide (SiC) and gallium nitride (GaN), aluminum nitride (ALN), gallium oxide (Ga2O3), etc., because the forbidden band width is greater than 2.2eV collectively referred to as wide-band semiconductor materials, also known as the third generation of semiconductor materials in China.
Discovery of Silicon Carbide
The first discovery of silicon carbide in the history of mankind was in 1891, the American Acheson in the electrolysis of diamond found a carbon compound, which is the first synthesis and discovery of silicon carbide. Subsequently, scientists from various countries after in-depth research, finally sorted out the advantages and characteristics of silicon carbide and invented a variety of silicon carbide long crystal technology, industrial research before and after up to more than 70 years.
In 2001, Infineon made the first silicon carbide diode, and then Cree, Rohm, ST and other companies entered the field of silicon carbide, silicon carbide diodes, transistors, MOSFET tubes, etc., there are a small number of scientific research institutes with the research and development of the IGBT structure of silicon carbide, but the structure of the IGBT can not be found in the application of the scene at a moment. Previously, we all know that silicon carbide is very good, but there are many problems, the first long crystal technology is immature, with too many defects in the crystal, seriously affecting the yield and stability, reliability; secondly, we do not know the application of the scene, because although the performance of the silicon carbide device is strong, but it’s too expensive, can not find a very suitable commercial landing.
But this is all changed by Tesla, Tesla is the first car company in the industry to propose the use of silicon carbide to replace silicon, and boldly used in Tesla’s Model 3, following other car manufacturers have followed suit, silicon carbide in large-scale on-board stage, so the industry believes that the first year of development of silicon carbide is in 2019, and Tesla’s this bold move opened the prelude to the high-speed development of carbonization.
Electrical Performance Advantages of Silicon Carbide Power Devices
- High voltage withstands: Critical breakdown electric field up to 2MV/cm (4H-SiC), and therefore has a higher voltage withstand capability (10 times that of Si).
- Easy heat dissipation: Due to the high thermal conductivity of SiC material (three times that of Si), heat dissipation is easier and the device can work at higher ambient temperatures. Theoretically, SiC power devices can operate at a junction temperature of 175°C, so the size of the heat sink can be significantly reduced.
- Low conduction and switching losses: SiC material has twice the electron saturation rate of Si, resulting in SiC devices with extremely low on-resistance (1/100 on Si) and low conduction losses; SiC material has a forbidden bandwidth of three times that of Si, and leakage currents are several orders of magnitude lower than those of Si devices. SiC material has three times the bandwidth of Si, the leakage current is reduced by several orders of magnitude compared to Si, thus reducing the power loss of the power device; there is no current trailing phenomenon in the shutdown process, low switching losses, can greatly improve the switching frequency of the actual application (10 times more than the Si).
- Reduce the size of the power module: due to the high current density of the device (e.g., Infineon products up to 700A/cm), in the same power level, the whole SiC The package size of all-SiC power modules (SiC MOSFETsSiC SBD) is significantly smaller than that of Si IGBT power modules at the same power level.
Major Disadvantages:The major disadvantage of Schottky diodes is the relatively high reverse current. Due to its metal-semiconductor junction, it is more prone to leakage currents when the voltage is connected in the reverse direction. In addition, Schottky diodes tend to have a low maximum reverse voltage. They tend to have a maximum value of 50V or less. Keep in mind that the reverse voltage is the value at which the diode will breakdown and begin to conduct a large amount of current when the voltage is connected in the reverse direction (from the cathode to the anode). This means that a Schottky diode cannot withstand a large reverse voltage without breaking down and conducting a large amount of current. It will still leak a small amount of current even before it reaches its maximum reverse value. Depending on the application and use of the circuit, this may prove to be significant or insignificant.