SiC Transistors - (VJFET)

Currently the JFET is the preferred SiC switching device because of its low on-resistance, mature technology and extraordinary ruggedness. We are therefore concentrating on Vertical Junction FETs (VJFET) which have already demonstrated excellent static and dynamic behavior.

Static characteristic

(5.5 x 5.5mm prototype chip, 23.5mm² active area)

Normally-Off Cascode:

As VJFETs are normally-on components we are combining them with low voltage Si MOSFETs to cascodes. A cascode represents a normally-off transistor. It has the input characteristic of the low voltage MOSFET, the blocking is defined by the used VJFETs. Samples with up to 4.5kV were realized. By using MOSFETs with smart functionality these functions are also becoming available now for high voltage switches.

Taking into account the equivalent circuit of modern power MOSFETs (e.g. Fairchild Application note AN-7502) it becomes obvious that the Si-SiC cascode is a hybrid version of the monolythic MOSFET where the JFET part is formed by SiC.

For a comparison of the dynamic behavior fo JFETs and cascodes, please refer to

Mino, K., Herold, S., and Kolar, J.W.: A Gate Drive Circuit for Silicon Carbide JFET. Proceedings of the 29th Annual Conference of the IEEE Industry Electronics Society, Roanoke (VA), USA, Nov. 2 - 6, pp. 1162 - 1166 (2003). 

Experimental switching data of 3^rd generation 350mOhm /1200V SiC VJFETs are shown below (for two different temperatures).

VJFETs show an extraordinary high ruggedness in short circuit mode

as well as in avalanche operation (blue : Drain voltage, red - drain current, green gate voltage, yellow gate current).

PSpice Models (based and developed on Symetrix 5.3b platform - UPDATE July 2009

Download 1200V/400mOhm type : LIB_INF04-File 

Download 1200V/100mOhm type : LIB_INF06-File

 Usage of the INF06-Model : Use_of_INF06

Please click on the link with the left mouse button and choose SAVE or use the right buttom of your mouse and chosse SAVE TARGET AS.

Remark :

The model relates to devices packaged in TO220. Due to the preliminary status, we would appreciate any feedback regarding the model. For further information please feel free to send us your comments.