Conduction band parameters of ZnO

We calculated the ordinary and extraordinary imaginary part of the dielectric function close to and above the absorption edge of wurtzite ZnO. Comparison to experimental data at room temperature revealed three main contributing mechanisms: optical transitions involving discrete exciton states, excitonically enhanced interband optical transitions, and exciton–phonon complexes. In addition, we found Ep⊥=12.5eV, Ep∥=14.2eV, m0⊥∗=0.242, m0∥∗=0.210 for the principal values of the momentum matrix element and the electron effective mass at the band edge, respectively. We also observed that the conduction band is slightly nonparabolic and determined the corresponding coefficients.