Growth of non-polar Zn1-x Mg x O thin films with different Mg contents on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy

We report the growth and characterization of a series of non-polar Zn1-x Mg (x) O thin films with different Mg contents, which have been prepared on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy. Structural properties are anisotropic and surfaces of films show stripes running along the c-axis direction. The films exhibit atomically smooth surface with the minimal root mean square surface roughness of 0.36 nm. Non-polar Zn1-x Mg (x) O thin film is much easier to obtain pure a-plane single crystal orientation when Mg content is high. The quality of the non-polar Zn1-x Mg (x) O thin films is evidenced by X-ray diffraction (XRD) rocking curves full-width at half-maximum of 1,350 arcsec for the () reflection and 1,760 arcsec for the () reflection, respectively. Room temperature photoluminescence peak shifts monotonously from 3.29 to 3.56 eV as Mg content increases from 0 to 0.13. Alloying with Mg is found to widen the bandgap energy of the ZnO.