Anomalously anisotropic channel mobility on trench sidewalls in 4H-SiC trench-gate metal-oxide-semiconductor field-effect transistors fabricated on 8° off substrates

Abstract

Metal-oxide-semiconductor (MOS) channel properties in 4H-SiC trench-gate MOS field-effect transistors fabricated on 8° off substrates were characterized. The MOS channel was formed only on one side of the trench sidewalls. The MOS field effect transistor performance depended strongly on the MOS channel planes of (112¯0), (1¯1¯20), (11¯00), and (1¯100). The highest channel mobility of 43cm2∕Vs was obtained on (112¯0). However, only a half value of 21cm2∕Vs was observed on (1¯1¯20), which is the opposite face to (112¯0). The anomalously anisotropic channel mobility is discussed based on the deviation from the crystallographically accurate {112¯0} plane caused by the combination of substrate off angle and sloped trench sidewalls.