Simulation of SiC MESFET for high frequency power application

Abstract

The potential of silicon carbide (SiC) MESFETs for high frequency applications are investigated by analytical calculations and TCAD simulations (Synopsys Sentaurus). First, the dependence on transistor parameters as gate length, channel thickness on fT, fMAX, gm and MAG have been studied using analytic expressions. TCAD simulations using a calibrated simulator were then used to propose different means of improving the high frequency performance of SiC MESFETs. It has been suggested by others that the short-channel effects can be reduced if a thin and heavily doped channel layer is used. The presented work shows that this assumption is probably not correct. Changing the doping of the channel reduces the electron mobility, leading to high access resistors, and thus does not improve the high frequency performance. By changing lateral and vertical dimensions fmax increased 26%. The conclusion is that there are larger benefits from changing the lateral and vertical dimensions than changing the doping concentration of the channel. Finally, a new transistor topology using a low doped spacer layer is suggested, resulting in an improvement of 13% compared to a more standard topology.