High field-effect mobility with suppressed negative threshold voltage shift in 4H-SiC MOSFET with cerium oxide interfacial layer

Enhanced oxidation of the 4H-SiC surface in an oxygen-lean environment by a thin CeOx layer was confirmed. By capping with a 40 nm thick SiO2 layer on a 1 nm thick CeOx layer, the formation of the interfacial SiO2 layer was suppressed, and the growth of the capped SiO2 layer was observed instead. A high peak field mobility of 54 cm2 V−1 s−1 was obtained with the structure, which is higher than the commonly used thermally grown SiO2 layer with NO-based high-temperature annealing. Moreover, the threshold voltage kept higher than 2 V, which has an advantage over other mobility enhancement gate oxide formation processes.