Influences of biaxial strains on the vibrational and exciton energies in ZnO.

We have investigated the structural, optical, and vibrational properties of strained heteroepitaxial ZnO layers by high resolution x-ray diffraction, reflectivity, and Raman measurements. The ZnO layers were grown by metalorganic vapor phase epitaxy on sapphire substrates under varying growth conditions. A Poisson number of μ=0.303 and phonon deformation-potential parameters of a=-690 cm^-1, b=-940 cm^-1 for the high-energy E₂ optical phonon mode have been determined. The shift of the excitonic resonances due to the strain in the layers agrees well with the experimentally determined Poisson ratio using the deformation-potentials D₁–D₄ determined by Wrzesinski and Fröhlich [Phys. Rev. B 56, 13087 (1997)]. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]