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In this work we report optical experiments on pseudomorphic cubic In x Ga 1−x N epilayers grown on cubic GaN/3C-SiC templates. We make a detailed study of photoluminescence (PL) and photoluminescence excitation spectroscopy on these samples, with spectra taken at various temperatures (between 2 K and 300 K) and using variable wavelength sources to excite the PL spectra. The combined use of these techniques suggests the existence of indium-rich clusters, constituting a negligibly small fraction of the volume of the total layer. Our results reinforce the notion that the large Stokes-like shift (a difference of approximately 300 meV between emission and absorption) observed in these samples is due to the fact that light absorption occurs in the bulk alloy of average composition while recombination occurs within the indium-rich clusters.

Magnetic nanoparticles (NPs) are especially interesting for several biomedical applications due to their chemical surface, especially for targeted cancer imaging and therapeutics.

We performed optical and x-ray diffraction experiments on carbon doped cubic-GaN samples, deposited by plasma-assisted molecular beam epitaxy on ͑001͒ GaAs substrates, for various carbon concentrations. The samples were studied by Raman, photoluminescence, and photoluminescence excitation spectroscopies. These techniques give some insight into the mechanism of carbon incorporation in the material. Detailed analysis of these spectra leads to a picture in which carbon initially enters into N vacancies producing a marked improvement in the crystalline properties of the material. At higher concentrations it also begins to enter interstitially and form C complexes, with a consequent decrease of crystalline quality. This increase and later decrease of crystalline quality of our samples with the addition of C were also detectable in x-ray diffraction scans. A model calculation of the localized vibrations of the C atom in the GaN lattice allows for the interpretation of a feature in the Raman spectrum of some samples, which reinforces this view.