Scaling Between Channel Mobility and Interface State Density in SiC MOSFETs

The direct impact of the SiO₂/4H-SiC interface state density (D_it) on the channel mobility of lateral field-effect transistors is studied by tailoring the trap distribution via nitridation of the thermal gate oxide. We observe that mobility scales like the inverse of the charged state density, which is consistent with Coulomb-scattering-limited transport at the interface. We also conclude that the D_it further impacts even the best devices by screening the gate potential, yielding small subthreshold swings and poor turn-ON characteristics.