Continued development of GaN-based light emitting diodes is being hampered by constraints imposed by current non-native substrates. ZnO is a promising alternative substrate but it decomposes under the conditions used in conventional GaN metal organic vapor phase epitaxy ͑MOVPE͒. In this work, GaN was grown on ZnO / c-Al 2 O 3 using low temperature/pressure MOVPE with N 2 as a carrier and dimethylhydrazine as a N source. Characterization confirmed the epitaxial growth of GaN. The GaN was lifted-off the c-Al 2 O 3 by chemically etching away the ZnO underlayer. This approach opens up the way for bonding of the GaN onto a support of choice.

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We report the synthesis and characterization of colloidal nanocrystals consisting of ZnO doped with Tb3+ cations. Introducing the Tb3+ cations in ZnO nanosized hosts led to photoluminescent systems whose wavelength emission depends on the excitation line. Chemical surface modification of the doped ZnO nanocrystals associated with photoluminescence studies allows us to conclude that Tb3+ cations are located in the ZnO core.

AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3 ϫ 10 14 to 1.4ϫ 10 17 atoms/ cm 2 in two different geometries: "channeled" along the c-axis and "random" with a 10°angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the channeled implantation within the entire fluence range. For random implantation, a buried amorphous layer is formed at the highest fluences. Red Eu-related photoluminescence at room temperature is observed in all samples with highest intensities for low damage samples ͑low fluence and channeled implantation͒ after annealing. Implantation damage, once formed, is shown to be stable up to very high temperatures.

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