Investigation of Al2O3 and TiO2 as gate insulators for 4H-SiC pulsed power devices

Achieving high quality and high electric breakdown of oxide on 4H-SiC substrates is still a major research challenge. 500 Å Al₂O₃ and TiO₂ were deposited on 4H-SiC by high vacuum and low-temperature e-beam evaporation. AFM (atomic force microscopy) results show that a surface mean height of 4-7 Å of Al₂O₃ was found on Si substrate and 74 Å of Al₂O₃ was found on SiC substrate. MIS capacitors were fabricated using one mask to evaluate the quality of these gate materials. C-V measurements at 10 kHz show that Al₂O₃ and TiO₂ have dielectric constants of more than 9 and 20, respectively. The leakage current of an Al₂O₃ MIS capacitor is about 10^-9 A on a capacitor area of 150 μm × 150μm at a gate voltage of ±10 V. An Al₂O₃ MIS capacitor has a lower leakage current than a TiO₂ MIS capacitor due to its large band gap offsets. Its breakdown electric field strength is more than 8 MV/cm. This research indicates that e-beam deposited Al₂O₃ may be a promising dielectric material for the pulsed power SiC devices.