Remarkable Increase in the Channel Mobility of SiC-MOSFETs by Controlling the Interfacial $\hbox{SiO}_{2}$ Layer Between $\hbox{Al}_{2}\hbox{O}_{3}$ and SiC

The impact of a thin $\hbox{SiO}_{2}$ layer inserted between $\hbox{Al}_{2}\hbox{O}_{3}$ and SiC on channel mobility in $\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiC}$ MOSFETs was investigated. The remarkable increase in the channel mobility is demonstrated when the $\hbox{SiO}_{2}$ thickness is around 1 nm. The thin $ \hbox{SiO}_{2}$ layer is formed by the thermal oxidation of the SiC substrate at 600 or 800 $^{\circ}\hbox{C}$ in $ \hbox{O}_{2}$ atmosphere. The peak value of the field-effect mobility in $\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiO}_{2}/\hbox{SiC}$ MOSFETs is as high as 300 $\hbox{cm}^{2}/\hbox{(V}\cdot\hbox{s)}$. On the other hand, when the $\hbox{SiO}_{2}$ layer is 2.0 nm, the field-effect mobility drastically reduces to 40 $\hbox{cm}^{2}/\hbox{(V}\cdot \hbox{s)}$, which is most likely due to the high interface trap density as seen in conventional $\hbox{SiO}_{2}/\hbox{SiC}$ MOSFETs.