Growth of high quality Zn0.9Mg0.1O films on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy

We report the growth and characterization of single-crystalline, epitaxial Zn0.9Mg0.1O films on c-plane sapphire substrates with MgO buffer layer by plasma-assisted molecular beam epitaxy. The quality of the Zn0.9Mg0.1O epilayers is evidenced by a Hall mobility of more than 60 cm2 V−1 s−1 at room temperature and an X-ray diffraction (XRD) rocking curve full-width at half-maximum of 47 arcsec for the (0 0 0 2) reflection. A screw dislocation density of 4 × 106 cm−2 is estimated by XRD. Transmission electron microscopy revealed that the thickness of the MgO buffer layer is about 3.5 nm, and a highly c-axis oriented Zn0.9Mg0.1O (0 0 0 2) reflection corresponding to the wurtzite-phase is observed. Alloying with Mg is found to widen the bandgap energy of the ZnO, and luminescence is observed at 3.502 eV at low temperature.