Epitaxial MgO buffer layers for YBa2Cu3O7−x thin film on GaAs

Epitaxial MgO thin films have been grown on GaAs using electron beam (e-beam) evaporation. X-ray diffraction indicates that the epitaxial relations are MgO[001]//GaAs[001] and MgO[110]//GaAs[110]. The rocking curve widths are less than 1.5°. The refractive index is 1.73 and the dielectric strength is in excess of 4×106 V/cm. The MgO epitaxial films were used as a buffer layer for the growth of in situ YBa2Cu3O7−x on GaAs. The room-temperature resistivity of this film is 450–530 μΩ cm and Tc (R=0) is 85–87 K. The critical current density at 77 K is 4–6.7×104 and 1–3.8×106 A/cm2 at 4.2 K, in zero applied field.