Band Offsets at the $\mathrm{Si}/{\mathrm{SiO}}_2$ Interface from Many-Body Perturbation Theory

We use many-body perturbation theory, the state-of-the-art method for band-gap calculations, to compute the band offsets at the $\mathrm{Si}/{\mathrm{SiO}}_2$ interface. We examine the adequacy of the usual approximations in this context. We show that (i) the separate treatment of band structure and potential lineup contributions, the latter being evaluated within density-functional theory, is justified, (ii) most plasmon-pole models lead to inaccuracies in the absolute quasiparticle corrections, (iii) vertex corrections can be neglected, and (iv) eigenenergy self-consistency is adequate. Our theoretical offsets agree with the experimental ones within 0.3 eV.

Figure 1

Difference between DFT and $\mathrm{QS}GW$ calculations for model III of (a) the planar average of the electronic density and (b) the macroscopic average of the local potential. The density is expressed in $\mathrm{m}e/\mathrm{a}.\mathrm{u}.$, and the potential in meV.