Growth study of nonpolar Zn_1−xMg_xO epitaxial films on a-plane bulk ZnO by plasma-assisted molecular beam epitaxy

Nonpolar $Zn1−xMgxO$ epitaxial films were grown by plasma-assisted molecular beam epitaxy on a-plane ZnO substrates. A smooth surface morphology was accomplished under oxygen-rich growth conditions. The benefits of the use of ZnO substrates on the structural properties are reflected by a low-density of threading dislocations. Furthermore, no indications for the generation of basal plane stacking faults are found. The pseudomorphic growth on a-plane ZnO substrates efficiently locks the epitaxial $Zn1−xMgxO$ films to the wurtzite structure up to x = 0.25. The Mg concentration is not constant and increases with larger thickness. The optical properties reflect the influence of alloy disorder.