Today a main focus in high efficiency power electronics based on silicon carbide (SiC)
lies on the development of an unipolar SiC switch. This paper comments on the advantages of SiC
switching devices in comparison to silicon (Si) switches, the decision for the SiC JFET against the
SiC MOSFET, and will show new experimental results on SiC JFETs with focus on the production
related topics like process window and parameter homogeneity which can be achieved with the
presented device concept.
Due to material properties unipolar SiC switches have, other than their Si high voltage counterparts,
very low gate charge, good body diode performance, and reduced switching losses because of the
potential of lower in- and output capacitances. The most common unipolar switch is the MOSFET.
However, the big challenge in the case of a SiC MOSFET is the gate oxide. A gate oxide on SiC
that provides adequate performance and reliability is missing until now. An alternative unipolar
switching device is a normally-on JFET. The normally-on behavior is a benefit for current driven
applications. If a normally-off behavior is necessary the JFET can be used together with a low
voltage Si MOSFET in a cascode arrangement. Recently manufactured SiC JFETs show results in
very good accordance to device simulation and demonstrate the possibility to fabricate a SiC JFET
within a mass production. A growing market opportunity for such a SiC switch becomes visible.
