Epitaxial growth of cubic Mg0.45Zn0.55O thin films on SrTiO3 (001) substrate with MgO buffer layer

Cubic Mg0.45Zn0.55O thin films with MgO buffer layer were epitaxially grown on SrTiO3 substrate by radio frequency oxygen plasma assisted molecular beam epitaxy. X-ray diffraction measurements indicate high quality single crystal films of (200) orientation. The growth follows cubic-on-cubic alignment with epitaxial relationship of Mg0.45Zn0.55O (001)[100]//MgO (001)[100]//SrTiO3 (001)[100]. Atomic force microscopy measurements reveal a smooth surface with the rms roughness of 0.36 nm in an area of 5×5 μm2. The band gap of the film is calculated to be 4.8 eV and in the solar blind range. Since the MgO buffer layer can suppress the sub-band-gap photoresponse from the SrTiO3 substrate and does not absorb moisture like the bare MgO substrate, the Mg0.45Zn0.55O thin films with MgO buffer layer grown on SrTiO3 substrate have promising applications in solar blind ultraviolet photodetectors.