Epitaxial YBa2Cu3O7 - delta on GaAs(001) using buffer layers

Epitaxy of YBa₂Cu₃O_7-δ (YBCO) on GaAs substrates has been demonstrated using epitaxial buffer layers. Recently developed methods for growing epitaxial YBCO thin films on Si have been adapted to achieve similar results on GaAs. MgO thin films were grown epitaxially on GaAs at below 400 °C. This layer provides a suitable template for the growth of YBCO or YBCO on BaTiO₃. All materials are deposited in situ by pulsed laser deposition in a single growth process. The in-plane crystallography of MgO on GaAs is [100] parallel to [100], accommodating a lattice mismatch of -25.5%. Zero resistance at temperatures as high as 87 K and transition widths as narrow as 1.5 K are reported. Critical current densities as high as 9×10⁶ A/cm² at 4.2 K and 1.5×10⁵ A/cm² at 77 K have been measured.