High I_on/I_offratio 4H-SiC MISFETs with stable operation at 500 °C using SiO₂/SiN_x/Al₂O₃gate stacks

In this work, 4H-SiC lateral metal-insulator-semiconductor field-effect transistors (MISFETs) were demonstrated to operate up to 500 °C with a high on/off current ratio (over 109). A low off-state current of 3.6 × 10-9 mA/mm at 500 °C was obtained in SiC MISFET with a ring structure. The MISFETs with SiO2/SiNx/Al2O3 gate dielectric stack showed minimum subthreshold swings of 155 and 240 mV/dec at room temperature and 500 °C, respectively, indicating good thermal stability of this gate dielectric stack on SiC. An interface trap density of 1.3 × 1011 cm-2 eV-1 at E - EV = 0.2 eV was extracted from the Capacitance-Voltage (CV) measurements at room temperature, which confirms excellent dielectric interface. The electron mobility increases with increasing temperature and reaches 39.4 cm2/V s at 500 °C. These results indicate that SiC MISFETs with triple layer dielectrics and ring structure have a high potential in extreme-temperature electronics.