ENHANCING POWER ELECTRONIC DEVICES WITH WIDE BANDGAP
Silicon carbide (SiC) unipolar devices have much higher breakdown voltages than silicon (Si) unipolar devices because of the ten times greater electric field strength of SiC compared with Si. 4HSiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4H-SiC compared to other polytypes. In this paper, four commercially available SiC Schottky diodes with different voltage and current ratings, VJFET, and MOSFET samples have been tested to characterize their performance at different temperatures ranging from −50°C to 175°C. Their forward characteristics and switching characteristics in this temperature range are presented. The characteristics of the SiC Schottky diodes are compared with those of a Si pn diode with comparable ratings
Keywords: SiC; MOSFET; JFET; Schottky diode.
With the increase in demand for more efficient, higher power, and higher temperature operation of power converters, design engineers face the challenge of increasing the efficiency and power density of converters. Development in power semiconductors is vital for achieving the design goals set by the industry. Si power devices have reached their theoretical limits in terms of higher temperature and higher power operation by virtue of the physical properties of the material. To overcome these limitations, research has focused on wide band gap materials, such as silicon carbide (SiC), gallium nitride (GaN), and diamond because of their superior material advantages such as large band gap, high thermal conductivity, and high critical breakdown field strength.
Diamond is the ultimate material for power devices because of its more than ten-fold better electrical properties; however, the diamond manufacturing process is still in its infancy. Considering that SiC (which is produced at much lower temperature) has many material issues, it is expected that diamond will have more materials issues. Diamond power devices might be available in a 20-50 year time frame. GaN and SiC power devices have similar performance improvements over Si power devices. GaN performs only slightly better than SiC. Both SiC and GaN have processing issues that need to be solved before they can seriously challenge Si power devices; however, SiC is at a more technically advanced stage than GaN. SiC is concluded to be the best suitable transition material for future power devices before high power diamond device technology matures. Since SiC power devices have lower losses, SiC-based power converters are more efficient. With the high temperature operation capability of SiC, thermal management requirements are reduced; therefore, a smaller heatsink would be sufficient. In addition to this, since SiC power devices can be switched at higher frequencies, smaller passive components are required in power converters. Smaller heatsink and passive components result in higher power density power converters. SiC unipolar devices such as Schottky diodes, VJFETs, and MOSFETs have much higher breakdown voltages compared with their Si counterparts, which makes them suitable for use in medium-voltage applications. At present, SiC Schottky diodes are the only commercially available SiC devices. SiC Schottky diodes are being used in several applications and have proved to increase the system efficiency compared with Si device performance. Significant reduction in weight and size of SiC power converters with an increase in the efficiency is projected. In the literature, the performance of SiC converters has been compared to traditional Si converters and was found to be better than Si power converters. The gate drive is an important aspect of the converter design which contributes to the device performance and hence the system....
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