Optical properties of epitaxially grown zinc oxide films on sapphire by pulsed laser deposition

ZnO thin films were epitaxially grown on c-sapphire substrates by pulsed laser deposition at substrate temperatures of 500-800 degrees C. The crystal structure of ZnO films follow the epitaxial relationship of (0001)(ZnO)<parallel to>(0001)(Al2O3)(10 (1) over bar 0)(ZnO)<parallel to>(11 (2) over bar 0)(Al2O3). Both room temperature and cryogenic temperature photoluminescence showed a remarkable band-edge transition, and clear excitonic structures could be seen at cryogenic temperature. The optical refractive index was measured in the range of 375-900 nm by varying angle spectroscopic ellipsometry. The simulation was carried out using a Sellmeier equation. (C) 1999 American Institute of Physics. [S0021-8979(99)02713-9].