Structural, optical, and surface acoustic wave properties of epitaxial ZnO films grown on (0112) sapphire by metalorganic chemical vapor deposition

High-quality ZnO films are receiving increased interest for use in low-loss high-frequency surface acoustic wave (SAW) devices, acousto-optic and optical modulators, as buffer layers for III-nitride growth, and as the active material in ultraviolet solid state lasers. In this work, high quality epitaxial ZnO films were grown on R-plane sapphire substrates by metalorganic chemical vapor deposition. The structural, piezoelectric, and optical properties of the ZnO films on R sapphire have been investigated. The epitaxial relationship between ZnO and R-Al2O3 was found to be (1120) ZnO∥(0112) Al2O3, and [0001] ZnO∥[0111] Al2O3. The interface between as-grown ZnO and R sapphire was atomically sharp and semicoherent, as evaluated by transmission electron microscopy. On annealing the films at temperatures above 850 °C, a solid state reaction occurred between ZnO and Al2O3, resulting in the formation of ZnAl2O4 (spinel) at the interface. A 15–20 nm spinel layer formed when the ZnO film was annealed at 850 °C fo...

[1]  T. Sekiguchi,et al.  Effect of Hydrogenation on ZnO Luminescence , 1997 .

[2]  Masashi Kawasaki,et al.  Ultraviolet spontaneous and stimulated emissions from ZnO microcrystallite thin films at room temperature , 1997 .

[3]  A. P. Roth,et al.  Properties of zinc oxide films prepared by the oxidation of diethyl zinc , 1981 .

[4]  S. Rushworth,et al.  Recent developments in metalorganic precursors for metalorganic chemical vapour deposition , 1995 .

[5]  D. Clarke,et al.  Epitaxial Aluminum‐Doped Zinc Oxide Thin Films on Sapphire: I, Effect of Substrate Orientation , 1995 .

[6]  J. Janek,et al.  Chemical kinetics of phase boundaries in solids , 1998 .

[7]  P. Wright,et al.  Metalorganic chemical vapour deposition of wide band gap II–VI compounds , 1984 .

[8]  Matthew T. Johnson,et al.  Thin-Film Reactions , 1998 .

[9]  D. C. Reynolds,et al.  Optical properties of GaN grown on ZnO by reactive molecular beam epitaxy , 1997 .

[10]  W. Y. Liang,et al.  Transmission Spectra of ZnO Single Crystals , 1968 .

[11]  T. Shiosaki,et al.  Low-loss epitaxial ZnO optical waveguides on sapphire by rf magnetron sputtering , 1987 .

[12]  F. Hickernell,et al.  Zinc Oxide Films for Acoustoelectric Device Applications , 1985, IEEE Transactions on Sonics and Ultrasonics.

[13]  P. W. Tasker,et al.  The stability of ionic crystal surfaces , 1979 .

[14]  Michael G. Spencer,et al.  Heteroepitaxy of ZnO on GaN and its implications for fabrication of hybrid optoelectronic devices , 1998 .

[15]  W. C. Hughes,et al.  MBE growth and properties of ZnO on sapphire and SiC substrates , 1996 .

[16]  S. Oktyabrsky,et al.  Defects and interfaces in epitaxial ZnO/α-Al2O3 and AlN/ZnO/α-Al2O3 heterostructures , 1998 .

[17]  H. Morkoç,et al.  Microstructure and optical properties of epitaxial GaN on ZnO (0001) grown by reactive molecular beam epitaxy , 1998 .

[18]  H. Morkoç,et al.  Formation of threading defects in GaN wurtzite films grown on nonisomorphic substrates , 1995 .