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 E 2 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 D 1 –D 4 determined by Wrzesinski and Fröhlich [Phys. Rev. B 56, 13087 (1997)].