Oxygen pressure-tuned epitaxy and optoelectronic properties of laser-deposited ZnO films on sapphire

Influence of oxygen pressure on the epitaxy, surface morphology, and optoel ectronic properties has been studied in the case of ZnO thin films grown on sapphire (0001) by pulsed-laser deposition. Results of Rutherford backscat tering and ion channeling in conjunction with atomic force microscopy clear ly indicate that the growth mode, degree of epitaxy, and the defect density strongly depend on the oxygen background pressure during growth. It is als o found that the growth mode and the defects strongly influence the electro n mobility, free-electron concentration, and the luminescence properties of the ZnO films. By tuning the oxygen pressure during the initial and the fi nal growth stages, smooth and epitaxial ZnO films with high optical quality , high electron mobility, and low background carrier concentration have bee n obtained. The implication of these results towards the fabrication of sup erlattices and controlled n- and p-type doping is discussed. (C) 1999 Ameri can Institute of Physics. [S0003-6951(99)01951-8].