First principles calculation of strain effects on the density of interface states in 4H-SiC

Even though the interface of SiO2/SiC can be improved by performing nitridation processes, it is unclear how interfacial traps are decreased or why this reduces the flat-band voltage. To discover the physical origin of the correlation between the SiO2/SiC interface traps and the oxidation processes, the effects of biaxial strain on the bandgap (Eg) of SiO2/4H-SiC (0001) were studied by first-principles calculations of the Heyd–Scuseria–Ernzerhof (HSE06) mixing function, with results closely corresponding to the experimental Eg of 4H-SiC. The compressive and tensile strains led to a change not only in the Eg, described in previous work but also in the total energy E0 of SiO2/4H-SiC (0001), where the structure reaches equilibrium at 2 % compression. We discussed in more detail that the size of the Eg is mainly affected by the O 2p state in SiO2 and the C 2p and Si 3p state in SiC in our works. These results indicate that the strain method can be used to adjust the Eg of SiO2/4H-SiC, thereby changing its interface state.