The glorious gate oxide

Should one worry about the lifetime of the gate oxide of SiC power MOSFETs under negative gate stress? Absolutely not, now that experiments show that they last as long as they do under a positive gate stress.

BY SATYAKI GANGULY, BRETT HULL, DANIEL LICHTENWALNER AND JOHN PALMOUR FROM WOLFSPEED

One of the greatest strengths of the 4H form of SiC is an electric breakdown field that is around ten times that of silicon. This means that for a given voltage rating, SiC power devices can feature a thinner drift region and higher doping than their silicon counterparts. In turn, this allows SiC power devices to have a far lower on-resistance (see Figure 1) and a simple unipolar MOSFET structure – there’s no need for complex architectures, involving super-junctions or bipolar conduction. On top of this, SiC power devices have low leakage currents at relatively high temperatures, and a high thermal conductivity that supports higher current densities, enabled by the low on-resistance.