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

Abstract

Mg_0.50Zn_0.50O 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 Mg_xZn_1−xO films are around 50%, independent of the growth substrates. X-ray diffraction measurements reveal that the lattice structures of these Mg_0.50Zn_0.50O 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-Mg_0.50Zn_0.50O is located in the UV-C (200–280 nm) region, while that of W-Mg_0.50Zn_0.50O is located in the UV-B (280–320 nm) region. Though Mg compositions of the Mg_0.50Zn_0.50O films are the same, the energy-band gap of the C-Mg_0.50Zn_0.50O film (5.1 eV) is much larger than that of the W-Mg_0.50Zn_0.50O 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-Mg_0.50Zn_0.50O and W-Mg_0.50Zn_0.50O films, respectively.