Epitaxial growth of high-quality Mg _x Zn _1-xO films by a plasma-assisted reactive evaporation method using ZnMg alloys as a source material

Epitaxial growth of high-quality Mg _x Zn _1-xO films on Zn faces of single crystal ZnO substrates was achieved by a plasma-assisted reactive evaporation method using ZnMg alloys. The composition of Mg of Mg _x Zn _1-xO films grown by using this method strongly depended on the composition of Mg of ZnMg alloys. Mg composition of Mg _x Zn _1-xO films increased with increase in the composition of Mg of ZnMg alloys with 7.5-30 wt%. The maximum value of (x) of the Mg _x Zn _1-xO films was 0.24. The peak position of XRD from Mg _x Zn _1-xO (0002) of a wurtzite structure shifted to a high angle with increase of Mg composition of Mg _x Zn _1-xO films. The full-width at half-maximum value of the XRD pattern of ω scans of Mg _0.17Zn0 _0.83O (0002) was 40 arcsec. The root mean square roughness of the surface of Mg _x Zn _1-xO films was 1.0 nm or less, and flat terraces and steps with a height of two monolayers were observed. Room temperature photoluminescence spectra of Mg _x Zn _1-xO films showed a strong near band-edge (NBE) emission and very weak emission in visible regions. The peak of NBE emissions of Mg _x Zn _1-xO films shifted to higher energy with increase of Mg composition of Mg _x Zn _1-x O films. The band-gap energy estimated from reflectance spectra increased from 3.38 to 3.83 eV with increase of composition (x) of Mg _x Zn _1-xO films from 0.01 to 0.24. This new growth method is useful for preparation of devices based on ZnO and its related compounds.