Real-structure effects: Absorption edge of MgxZn1-xO, CdxZn1-xO, and n-type ZnO from ab-initio calculations

The continuously increasing power of modern supercomputers renders the application of more and more accurate parameter-free models to systems of increasing complexity feasible. Consequently, it becomes possible to even treat different real-structure effects such as alloying or n-doping in systems like the technologically important transparent conducting oxides. In this paper we outline how we previously used a combination of quasiparticle calculations and a cluster expansion scheme to calculate the fundamental band gap of MgxZn1-xO and CdxZn1-xO alloys. We discuss the results in comparison to values for In2O3, SnO2, SnO, and SiO2. In addition, we discuss our extension of the Bethe-Salpeter approach that has been used to study the interplay of excitonic effects and doping in n-type ZnO. The dependence of the Burstein-Moss shift on the free-carrier concentration is analyzed.