Lateral grain size and electron mobility in ZnO epitaxial films grown on sapphire substrates

We have fabricated ZnO thin films on sapphire substrates at temperatures ra nging from 350 to 1000 degrees C by laser molecular-beam epitaxy. With incr easing growth temperature, lateral grain size evaluated by X-ray reciprocal space mapping increased resulting in improved electron mobility. When the film was grown at 1000 degrees C, an electron mobility as large as 90 cm(2) /Vs was achieved. By annealing in 1 atm of oxygen at 1000 degrees C, thin f ilms having much larger grain size (> 5 mu m(2)) and higher mobility(simila r to 120 cm(2)/V s) comparable with those for bulk single crystals could be obtained. (C) 2000 Elsevier Science B.V. All rights reserved.