EPITAXIAL-GROWTH OF ALUMINUM-DOPED ZINC-OXIDE FILMS ON (1120) ORIENTED SAPPHIRE SUBSTRATES

ZnO:Al films were deposited on (1120BAR) oriented sapphire substrates heated up to 400-degrees-C with an RF power ranging from 25 to 170 W by RF magnetron sputtering from a ZnO target mixed with Al2O3 of 2 wt%. Films deposited on substrates heated to a temperature in the range 50-350-degrees-C were (0001) oriented single crystals but those grown at 400-degrees-C consisted of crystallites with the (0001) and (1011BAR) orientation. The epitaxial relationships between ZnO:Al films and the substrates were determined by using the reflective electron diffraction patterns from the films and the back-reflection Laue patterns from the substrates. From these measurements, it was found that there were two types of epitaxial relationships between the (0001) ZnO:Al films and the (1120BAR) sapphire substrates. One was [1010BAR]ZnO:Al parallel-to [0001]sapphire and the other [2110BAR]ZnO:Al parallel-to [0001]sapphire.