In this work, we investigated the static characteristics of 4H-SiC vertical metal-oxide- semiconductor field effect transistors (VMOSFETs) by adjusting the doping level of n-epilayer and the effect of a current spreading layer (CSL), which was inserted below the p-base region with highly doped n+ state (5 x 1017 cm-3). The structure of SiC VMOSFET was designed by using a 2-dimensional device simulator (ATLAS, Silvaco Inc.). By varying the n-epilayer doping concentration from 1×1016 cm-3 to 1×1017 cm-3, we investigated the static characteristics of SiC VMOSFETs such as blocking voltages and on-resistances. We found that CSL helps distribute the electron flow more uniformly, minimizing current crowding at the top of the drift region and reducing the drift layer resistance. For that reason, silicon carbide VMOSFET structures of highly intensified blocking voltages with good figures of merit can be achieved by adjusting CSL and doping level of n-epilayer.
