Band discontinuities at Si-TCO interfaces from quasiparticle calculations: Comparison of two alignment approaches

Abstract

Modern quasiparticle theory based on hybrid functionals and the $GW$approximation yields electronic band structures with a high accuracy for silicon but also for oxides applied as transparent electrodes or layers in solar cells. The quasiparticle electronic structures are used to derive natural band discontinuities applying two different methods, a modified Tersoff method for the branch-point energy and the Shockley-Anderson model via the electron affinity rule. For the known Si-SiO${}_{2}$ interface, which leads to type-I junctions, we demonstrate that both approaches are in good agreement with measured values. For the Si-oxide heterojunctions we observe a tendency for misaligned type-II heterostructures for In${}_{2}$O${}_{3}$, ZnO, and SnO${}_{2},$ which indicates highly efficient separation of electron-hole pairs generated in the Si layer. We show how surface orientation and structure as well as many-body effects influence the ionization energy and electron affinity and, hence, the band discontinuities obtained within the Shockley-Anderson model.