Effects of uniaxial stress on the electrical structure and optical properties of Al-doped n-type ZnO

To analyze the effect of uniaxial stress on the Al-doped ZnO, we investigated the parameters of electronic structure and optical properties such as band structure, density of states (DOS), dielectric constant, absorption coefficient and reflection spectra under different uniaxial stresses by using first-principles based on density functional theory (DFT). The results demonstrated that the lattice constants (a, c) vary linearly with changes of uniaxial stress. The band gaps are broadened with the decrease in the uniaxial tensile stress and with the increase in the uniaxial compressive stress. When the uniaxial stress is 5 GPa, the crystal field splitting energy reaches a minimum value. Meanwhile, the imaginary part of the dielectric function decreases with the increase in the uniaxial compressive stress with the energy lower than 5.9 eV. And it increases with the increase in the uniaxial compressive stress and appears a blueshift when the energy is higher than 5.9 eV. With the increase in the uniaxial compressive stress, absorption coefficient α(E), reflectance R(E), refractive index n(E), and energy loss spectroscopy L(E) all move to the higher energy direction (blueshift) and have a larger spectral peaks. This may imply a certain theoretical reference for the modulation of Al-doped n-type ZnO.