High-quality ZnO layers grown by MBE on sapphire

The development of Molecular Beam Epitaxy (MBE) of ZnO epilayers employing hydrogen peroxide (H2O2) as an oxidant is presented. ZnO layers were grown on (0001)Al2O3 in a modified Varian Gen II MBE system, with H2O2 as an oxygen precursor. Layers with thicknesses from 100 nm to 500 nm were obtained. The influence of growth parameters on structural properties as well as on surface morphology of the zinc oxide layers on sapphire is investigated and discussed. The quality of the layers was improved by employing a thin MgO buffer and a subsequently grown low-temperature ZnO buffer layer followed by the main ZnO layer at higher temperature. The surface toughness of the best ZnO layers is about 0.2 nm for a 2 x 2 mu m(2) AFM scan area. X-Ray Diffractometry (XRD) measurements of the ZnO layers obtained show excellent quality of the single-crystalline ZnO heteroepitaxially grown on sapphire. The FWHM of the XRD (0002) rocking curve is as low as 30 arcsec. The excellent quality of the ZnO epiwafers provides the possibility of eventually using them as an alternative to bulk ZnO wafers. (C) 2005 Elsevier Ltd. All rights reserved.