Investigations of ZnO Thin Films Grown on c-Al2O3 By Pulsed Laser Deposition in N2 + O2 Ambient

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ZnO films were deposited on c-Al2O3 using pulsed laser deposition both with and without N2 in the growth ambient. X-ray diffraction revealed poorer crystal quality and surface morphology for one-step growths with N2 in the ambient. A marked improvement in both the crystallographic and surface quality was obtained through use of two-step growths employing nominally undoped ZnO buffer layers prior to growth with N2 in the ambient. All films showed majority n-type conduction in Hall measurements. Post-annealing for 30 minutes at 600 ºC in O2 systematically reduced both the carrier concentration and the conductivity. A base room temperature carrier concentration of ∼ 1016 cm–3 was linked to Al diffusing from the substrate. 4.2 K photoluminescence spectra exhibited blue bands associated with the growths having N2 in the ambient. Temperature dependent Hall measurements were consistent with N being incorporated in the films. Processed devices did not, however, show rectifying behaviour or electroluminescence. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)


Special Issue: 34th International Symposium on Compound Semiconductors (ISCS-2007)