Characterization of 4H-SiC MOSFET Interface Trap Charge Density Using a First Principles Coulomb Scattering Mobility Model and Device Simulation

We have developed a physics based device simulator for detailed numerical analysis of 4H-SiC MOSFETs. As part of the drift diffusion model implemented in the simulator, a first principles quasi-2D Coulomb scattering mobility model for SiC MOSFETs has been developed. This Coulomb scattering mobility model takes into account scattering by occupied interface traps, scattering by fixed oxide charges, distribution of mobile carriers inside the inversion layer, screening by mobile carriers and temperature. Using this mobility model it has been shown that Coulomb scattering plays a dominant role very close to the interface. The interface trap density of states profile has been extracted by comparing simulated I-V curves to experimental data for room temperature. Simulations show that interface trap density of states is low in the midgap region and very high near the conduction band edge in 4H SiC, and it severely limits device performance.