Silicon and transparent conducting oxides: Si/ZnO and Si/In2O3 interfaces from first principles

The Transparent Conducting Oxides (TCOs) In2O3 and ZnO are routinely used as transparent electrodes in Si-based photovoltaics. Their interfaces with Si are consequently of great interest. Electronic band offsets, dangling bonds, and interface states determine the efficiency of charge-carrier separation in solar cells. Sample-preparation problems and difficulties in correctly describing the electronic properties of TCOs make the determination of these important quantities a challenging task to theoreticians and experimentalists alike. We develop a method for the construction of atomic models of heterostructural interfaces based on coincidence lattices, maximum bond saturation, and total energy minimization, which enables us to construct model geometries for the interface between Si and ZnO as well as between Si and In2O3. In particular we investigate the Si(001)/ZnO(20 anti 23) and the Si(001)/In2O3(001) interface by means of density functional theory (DFT) and modern quasiparticle theory based on semilocal exchange-correlation functionals. We examine electronic band discontinuities and interface states. The influence of dangling bond passivation, strain, and charge transfer is studied by their respective influence on the electronic density of states.