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

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The impact of a thin <formula formulatype="inline"><tex>$\hbox{SiO}_{2}$</tex></formula> layer inserted between <formula formulatype="inline"><tex>$\hbox{Al}_{2}\hbox{O}_{3}$</tex></formula> and SiC on channel mobility in <formula formulatype="inline"><tex>$\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiC}$</tex></formula> MOSFETs was investigated. The remarkable increase in the channel mobility is demonstrated when the <formula formulatype="inline"> <tex>$\hbox{SiO}_{2}$</tex></formula> thickness is around 1 nm. The thin <formula formulatype="inline"><tex>$ \hbox{SiO}_{2}$</tex></formula> layer is formed by the thermal oxidation of the SiC substrate at 600 or 800 <formula formulatype="inline"><tex>$^{\circ}\hbox{C}$</tex></formula> in <formula formulatype="inline"><tex>$ \hbox{O}_{2}$</tex></formula> atmosphere. The peak value of the field-effect mobility in <formula formulatype="inline"><tex>$\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiO}_{2}/\hbox{SiC}$</tex></formula> MOSFETs is as high as 300 <formula formulatype="inline"><tex>$\hbox{cm}^{2}/\hbox{(V}\cdot\hbox{s)}$</tex></formula>. On the other hand, when the <formula formulatype="inline"><tex>$\hbox{SiO}_{2}$</tex></formula> layer is 2.0 nm, the field-effect mobility drastically reduces to 40 <formula formulatype="inline"><tex>$\hbox{cm}^{2}/\hbox{(V}\cdot \hbox{s)}$</tex></formula>, which is most likely due to the high interface trap density as seen in conventional <formula formulatype="inline"><tex>$\hbox{SiO}_{2}/\hbox{SiC}$</tex></formula> MOSFETs. </para>