High Current Density Transient Conditions

For SiC DMOSFETs to obtain widespread usage in power electronics their long-term operational ability to handle the stressful transient current and high temperatures common in power electronics needs to be further verified. To determine the long-term reliability of a single 4H-SiC DMOSFET, the effects of extreme high current density were evaluated. The 4H-SiC DMOSFET has an active conducting area of 40 mm², and is rated for 1200 V and 150 A. The device was electrically stressed by hards-witching transient currents in excess of four times the given rating (>600 A) corresponding to a current density of 1500 A/cm².

Periodically throughout testing, several device characteristics including R_DS(on) and VG S(th) were measured. After 500 000 switching cycles, the device showed a 6.77% decrease in R_{DS (on)}, and only a 132-mV decreased in V_{G S(th)}. Additionally, the dc characteristics of the device were analyzed from 25 to 150 °C and revealed a 200-mV increase in on-state voltage drop at 20 A and a 2-V reduction in V_{G S(th)} at 150 °C. These results show this SiC DMOSFET has robust long-term reliability in high-powerapplications that are susceptible to pulse over currents, such as pulsed powermodulators and hard-switched power electronics.