Simulation of Surface State Effects in the Transient Response of 4H-SiC MESFETs

Two-dimensional small-signal ac and transient analyses of surface trap effects in 4H-SiC MESFETs have been performed in this paper. The mechanism of acceptor-type traps on transconductance and drain current changes has been discussed. The simulation results show that transconductance exhibits negative frequency dispersion behavior, which is caused by the charge exchange via the surface states existing between the gate-source and gate-drain terminals. The current degradation behavior is also observed due to acceptor-type traps, acting as electron traps, in MESFET devices. A detailed study about ionization and energy level of traps reveals conclusive results in the devices analyzed.