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.