Effect of higher conduction band on electron mobility in 4H-SiC inversion layers

Effects of the band structure parameters on the subband energies and the electron mobility in 4H-SiC inversion layers are studied theoretically. The bulk band structure of 4H-SiC is calculated using a first-principles pseudopotential method, and then electron effective masses in the two lowest conduction bands are obtained, which are used in the self-consistent calculation of the electronic states at the SiC/SiO₂ interface. It is shown that the higher-energy valley affects the mobility particularly under strong confinement condition, depending on the surface orientations.