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

Abstract

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)].