The potential of fast high voltage SiC diodes

Silicon carbide power devices offer important advantages compared to silicon devices, regarding higher power ratings at clearly reduced static and dynamical losses, better reliability because of possible higher operating temperatures, and significant savings in system cooling equipment. Physically, these benefits are mainly due to the wide band gap of SiC and the by an order of magnitude higher critical electric field. Consequently, the doping concentration will be by 2 orders of magnitude higher and the thickness of the devices about an order of magnitude lower for the same blocking voltage compared to silicon. Therefore, the power rating of unipolar devices such as Schottky diodes, vertical JFETs and MOSFETs is strongly extended to high voltage application. On the other side bipolar devices such as p-n diodes, IGBTs and thyristors will predominantly be used for applications, where blocking voltages considerably higher than 2000 V and/or increased operational temperatures are required. This is a consequence of their higher threshold voltage compared to Si. To clarify differences in the overall electrical behaviour, both types of diodes with blocking voltages below 2000 V should be analysed. In this paper we present the properties and limitations of 4H-SiC diodes and relate the experimental data of Schottky and p-n diodes with results obtained with the device simulator MEDICI