The SiC JFET Introduced by Semisouth

Published:2011/8/31 2:02:00 Author:Li xiao na From:SeekIC

A high-power silicon carbide JFETs is introduced by Semisouth which is located in Mississippi. The high-power silicon carbide JFETs is going to replace the silicon IGBTs and silicon mosfets in high power inverters. The SiC Schottky diodes have been made for the power factor correction and solar inverter markets. Using the power JFET seems very strange for a switching device, because enhancement mode power mosfets are always chosen. Like power mosfets and IGBTs, the Enhancement-mode devices are ’on’ when the gate is at zero volts. A negative bias is needed to turn them off. The new product of SemiSouth can provide the normally-off JFET. This function is not owned by the other devices.

A junction is created for the gate in a JFET. With the same current and voltage rating, the SiC JFET die are one tenth the size of Si mosfets and IGBTs. The JFET structure is a trench design. Semisouth is the first company to etch a trench in SiC. The seven mask process of the JFET is the same number of steps as an IGBT, although the steps are different. Without the minority carrier storage, rise and fall times are fast. They are 20 and 15ns respectively. The fast rise and fall times make the inverters be operated faster than silicon IGBT types. Higher frequency means smaller magnetics, but the designer is going to have to watch out for switching transients. A suggested opto-isolated gate driver, which is based around one Ixys IXDN404 4A dual driver chip per gate, has been issued by the firm.



With the transistors and more established SiC diodes, the solar inverter becomes the most exciting point of SemiSouth. Some other companies, such as Cree and Rohm, are trying to enter SiC mosfets. They will become the competitive rivals of SemiSouth. SiC Schottky diodes will be used in the boost converter stage of solar inverters to replace the fast high-voltage silicon diodes in the future days.

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