The non-radiative photoluminescence lifetime and point defect density in an (00▪1) ZnO epilayer grown onto (111)Si substrates, by laser-assisted molecular-beam epitaxy using a (00▪1) ZnS epitaxial buffer layer, were compared with those for ZnO films on (111) and (001) Si substrates; prepared by direct transformation of ZnS epilayers on Si by thermal oxidation. Both ZnO films exhibited excitonic reflectance anomalies and corresponding photoluminescence peaks at low temperature. The density or size of vacancy-type point defects (Zn vacancies), which were measured by mono-energetic positron annihilation in the laser-assisted molecular-beam epitaxy epilayer, were lower than those in films prepared by the oxidation transformation. The ZnO epilayer grown on a (00▪1) ZnS epitaxial buffer on (111) Si exhibited a longer photoluminescence lifetime (105ps) at room temperature.

Reduced Defect Densities in the ZnO Epilayer Grown on Si Substrates by Laser-Assisted Molecular-Beam Epitaxy using a ZnS Epitaxial Buffer Layer. T.Onuma, S.F.Chichibu, A.Uedono, Y.Z.Yoo, T.Chikyow, T.Sota, M.Kawasaki, H.Koinuma: Applied Physics Letters, 2004, 85[23], 5586-8