Isotropic Channel Mobility in UMOSFETs on 4H-SiC C-Face with Vicinal Off-Angle

UMOSFET is theoretically suitable to decrease the on-resistance of the MOSFET. In this study, in order to determine the cell structure of the SiC UMOSFET with extremely low on-resistance, influences of the orientation of the trench and the off-angle of the wafer on the MOS properties are investigated. The channel resistance, gate I-V curves and instability of threshold voltage are superior on the {11-20} planes as compared with other planes. On the vicinal off wafer, influence of the off-angle disappears and the properties on the equivalent planes are almost the same. The obtained results indicate that the extremely low on-resistance with the high stability and high reliability is possible in the SiC UMOSFET by the hexagonal cell composed of the six {11-20} planes on the vicinal off wafer, and actually an extremely low channel resistance was demonstrated on the hexagonal UMOSFET with the six {11-20} planes on the vicinal off wafer.