Modeling the Effect of Conduction Band Density of States on Interface Trap Occupation and Its Influence on 4H-SiC MOSFET Performance

Interface traps play a crucial role in determining total mobile charge available for conduction and also in determining low field mobility in 4H-SiC MOSFETs. They are important in determining current and transconductance in these devices. Accurate calculation of the interface trap density is essential for characterization of transport in 4H-SiC MOS devices. Typical conduction band edge density of states for traps can reach values comparable to electron states in the conduction band. Therefore, it is necessary to include traps located in the conduction band while calculating occupied trap densities. Using DOS calculated by DFT method, we show that trap and electron DOS are comparable up to 200 meV inside the conduction band, and use this to calculate occupied trap densities and currents for 4H-SiC MOSFETs. Validation of this occupation model is achieved by excellent comparison of simulated and measured current-voltage characteristics for MOSFETs with a wide range of channel doping values.