Based on the k.p theory of Luttinger-Kohn and Bir-Pikus,analytical E-k solutions for the valence band of strained wurtzite ZnO materials are obtained.Strain effects on valence band edges and hole effective masses in strained wurtzite ZnO materials are also discussed.In comparison with unstrained ZnO materials,apparent movement of valence band edges such as "light hole band","heavy hole band" and "crystal splitting band" at Γ point is found in strained wurtzite ZnO materials.Moreover,effective masses of "light hole band","heavy hole band" and "crystal splitting band" for strained wurtzite ZnO materials as the function of stress are given.The analytical results can provide a theoretical foundation for the understanding of physics of strained ZnO materials and its applications with the framework for an effective mass theory.
Band structures in wurtzite bulk ZnO/Zn1-xMgxO are calculated using first-principles based on the framework of generalized gradient approximation to density functional theory with the introduction of the on-site Coulomb interaction. Strain effects on band gap, splitting energies of valence bands, electron and hole effective masses in strained bulk ZnO are discussed. According to the results, the band gap increases gradually with increasing stress in strained ZnO as an Mg content of Znl-xMgxO substrate less than 0.3, which is consistent with the experimental results. It is further demonstrated that electron mass of conduction band （CB） under stress increases slightly. There are almost no changes in effective masses of light hole band （LHB） and heavy hole band （HHB） along [00k] and [k00] directions under stress, and stress leads to an obvious decrease in effective masses of crystal splitting band （CSB） along the same directions.
