MINIMUM THICKNESS MGO BUFFER LAYERS FOR YBA2CU3O7-X GAAS STRUCTURES -ASSESSMENT USING PHOTOLUMINESCENCE OF MULTIPLE-QUANTUM-WELL STRUCTURES/

A GaAs-AlGaAs multiple-quantum-well structure was used as a substrate for overgrowth by a MgO buffer layer and superconducting YBa2Cu3O7-X t hin film. The multiple quantum well serves as an in-depth probe for po ssible damage incurred by the semiconductor substrate due to the relat ively high temperature and active oxygen environment that characterize s the superconductor growth. The thickness of the MgO buffer layer was varied and correlated with both the superconducting properties of the overlying YBa2Cu3O7-X and the quality of the substrate as determined by photoluminescence measurements of the multiple quantum wells. Both high quality superconducting YBa2Cu3O7-X and excellent photoluminescen ce spectra of the substrate were obtained with a MgO thickness of 450 angstrom and quantum wells as close as 350 angstrom to the surface.