Investigation of Gate Leakage Current Behavior for Commercial 1.2 kV 4H-SiC Power MOSFETs

The commercialization of silicon carbide (SiC) power metal-oxide-semiconductor field-effect-transistors (MOSFETs) has expanded during the last decade. The gate oxide reliability is the primary issue for SiC power MOSFETs since it determines the device's operational lifetime. In this work, we investigate the gate leakage currents under different gate voltages on commercial 1.2 kV SiC power MOSFETs. The impact ionization and/or anode hole injection (AHI) triggered by high oxide electric fields results in hole trapping that enhances the gate leakage current and reduces device's threshold voltage. The electron injection and trapping due to Fowler-Nordheim (F - N) tunneling tend to reduce the gate leakage current and increases threshold voltage. Constant-voltage time-dependent dielectric breakdown (TDDB) measurements are also conducted on the commercial MOSFETs. The results on gate leakage current suggest that the change of the field acceleration factor is due to enhanced gate current/hole trapping under high gate oxide fields. Therefore, it is suggested that TDDB measurements should be conducted under low gate voltages to avoid overestimation of lifetime under normal operating gate voltage.