Evaluation of 4H-SiC DMOSFETs for power converter applications

Abstract

This paper presents an evaluation of state-of-the-art 1.2 kV 4H-SiC DMOSFETs for DC-DC power converter applications. Initial electrical measurements on large area DMOSFET die ~ 0.221 cm2 (4.7mm x 4.7mm) gives a low specific on-resistance (Rsp,on) of 17 Omega*cm2 for Vgs = 15 V at room temperature. The on-state characteristic for a packaged DMOSFET, where the drain-to-source on-resistance (Rds(on)) is measured to be 96 mOmega at room temperature and 94 mOmega at 150 degC at 20 A forward current. The inset of Figure 1 plots the measured Rds(on) values over a temperature range of 25 degC to 150 degC, demonstrating stable device operation. Although the MOS channel resistance at elevated temperatures is reduced due to the negative shift in threshold voltage (Figure 2), the total on-resistance of the device increases due to the decrease in mobility in the drift layer region. Figure 3 shows the DMOSFET drain leakage at temperature for 1.2 kV blocking with less than 30 muA of measurable current. Figure 4 shows the sub-threshold behavior with 1.8 V of gate bias needed to keep the drain current below 1 muA at 25 degC, as opposed to 1.3 V needed at 150 degC. To ensure normally-off operation a positive subthreshold voltage is desired.