Density functional and Monte Carlo-based electron transport simulation in 4H-SiC(0001)/SiO2 DMOSFET transition region

The potential presence of a transition layer at the SiC/SiO₂ interface may affect the electronic characteristics of SiC devices. Several experiments indicate the presence of C-O-Si bridges [1-3] at the interface. We investigated and compared the effect of possible interface structures on the total, and projected density, of states of the SiC/SiO₂ system with the use of density functional theory (DFT). We also utilized the Monte Carlo carrier transport modeling technique to obtain the average velocities and mobilities of each structure. The ionized impurity limited mobility of likely structures has been calculated. We constructed various structures with the forms of SiO_xC_y, and Si_1-xC_xO₂ in both SiC, and SiO₂ sides of the interface. According to our calculations, strong possible candidates for generating the traps near the conduction band are SiO_xC_y structures formed by replacing carbon atoms in SiC with oxygen. The overall mobility, and the ionized impurity limited mobility decrease as the number of O(C) in the SiC side of the SiO_xC_y structures increase. Moreover, the calculated ionized impurity limited mobility is less than 30 cm²/Vs in low external field.