Dependence of structural and optoelectronic properties of sputtered Mg0.50Zn0.50O films on substrate

Mg0.50Zn0.50O thin films were grown on MgO, sapphire and quartz substrates by a home-made magnetron sputtering system under the same deposition conditions. The Mg compositions in all these MgxZn1-xO films are around 50%, independent of the growth substrates. X-ray diffraction measurements reveal that the lattice structures of these Mg0.50Zn0.50O films depend on the lattice structures of growth substrates and are cubic (C), wurtzite (W) and mixed phase, respectively. Transmission spectra show that the cutoff wavelength of C-Mg0.50Zn0.50O is located in the UV-C (200-280 nm) region, while that of W-Mg0.50Zn0.50O is located in the UV-B (280-320 nm) region. Though Mg compositions of the Mg0.50Zn0.50O films are the same, the energy-band gap of the C-Mg0.50Zn0.50O film (5.1 eV) is much larger than that of the W-Mg0.50Zn0.50O film (4.3 eV) due to the different electronic structure between the cubic and wurtzite structures. Metal-semiconductor-metal structure solar-blind and visible-blind UV photodetectors were fabricated based on the C-Mg0.50Zn0.50O and W-Mg0.50Zn0.50O films, respectively.