Reliability investigation with accelerated body diode current stress for 3.3 kV 4H-SiC MOSFETs with various buffer epilayer thickness

3.3 kV 4H-SiC MOSFETs with various buffer layer thickness has been fabricated in order to investigate the bipolar degradation associated with the expansion of stacking faults (SFs). The body diode stress tests under DC current of 240 A/cm
²
were performed at 200 °C. Shifts in specific on-resistance (R
_{on, sp}
) and forward voltage (V
_f
) of body diode were markedly reduced for the MOSFETs with thick buffer layer of 30 μm. This result indicates that the body diode reliability may be improved by suitably designed buffer layer. The photoluminescence (PL) image of these SiC epilayer after the stress tests revealed the SF expansion due to the bipolar current stress was suppressed by the thick buffer layer.