Remarkable Increase in the Channel Mobility of SiC-MOSFETs by Controlling the Interfacial SiO₂ Layer Between Al₂O₃ and SiC

The impact of a thin SiO₂ layer inserted between Al₂O₃ and SiC on channel mobility in Al₂O₃/SiC MOSFETs was investigated. The remarkable increase in the channel mobility is demonstrated when the SiO₂ thickness is around 1 nm. The thin SiO₂ layer is formed by the thermal oxidation of the SiC substrate at 600 or 800 ∘C in O₂ atmosphere. The peak value of the field-effect mobility in Al₂O₃/SiO₂/SiC MOSFETs is as high as 300 cm²/(V⋯). On the other hand, when the SiO₂ layer is 2.0 nm, the field-effect mobility drastically reduces to 40 cm²/(V· s), which is most likely due to the high interface trap density as seen in conventional SiO₂/SiC MOSFETs.