Two-dimensional analysis of the surface state effects in 4H-SiC MESFETs

Two-dimensional small-signal ac and transient analysis of surface trap effects in 4H-SiC MESFETs have been performed in this paper. The mechanism by which acceptor-type traps effect the 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 involving the density, ionization and energy level of traps reveals conclusive results in the devices analyzed.