Epitaxial growth and stress analysis of Zn_1-xMg_xO films on (111) Si substrates

Zn_1-xMg_xO films with Mg content varied from 0 to 0.17 were fabricated on Lu₂O₃/(111) Si substrates by plasma-assisted molecular beam epitaxy. The crystal structure, optical and electrical properties of the as-grown Zn_1-xMg_xO films were investigated by X-Ray diffraction (XRD), photoluminescence and Hall-effect measurements. Highly c-axis preferred oriented hexagonal Zn_1-xMg_xO films with six-fold symmetry and tunable bandgap from 3.31 to 3.55 eV were identified. The lattice constants and residual stress were analyzed by XRD measurement and Raman spectra. A state of compressive uniaxial residual out-of-plane strain and tensile biaxial in-plane stress were confirmed. Besides, the phonon deformation-potential parameter was calculated and the value decreased as Mg content increasing. It indicates that Mg incorporation has effectively reduced oxygen vacancy. In addition to the use of determining residual stress, Raman spectroscopy is also turned out to be a useful supplementary analysis to investigate the intrinsic defects in thin films. - Highlights: • Zn_1-xMg_xO films were grown on Lu₂O₃/(111) Si substrates by molecular beam epitaxy. • Compressive out-of-plane strain and tensile biaxial in-plane stress were confirmed. • Value of phonon deformation-potential parameter decreased as Mg content increasing. • It is deduced that Mg incorporation has effectively reduced oxygen vacancy. • Raman spectroscopy can be used to analyze intrinsic defects except for stress study.