Nanostructured GaN: Microstructure and optical properties

In the present study, the microstructure and optical properties of a nanostructured composite that consists of nanocrystalline GaN imbedded in a poly(methyl methacrylate) thin film matrix (GaN/PMMA) are reported. X-ray powder diffraction and high-resolution transmission electron microscopy were performed to analyze the microstructure, while the optical properties were measured by optical absorption and photoluminescence. Microstructural analyses showed that GaN nanocrystallites imbedded in the PMMA matrix have a size of about 5.5 nm, and crystallize in the zinc-blende lattice (the lattice constant a(0) similar to 0.45 nm) with a considerable fraction of structural defects such as nitrogen; vacancies and stacking faults. Optical-absorption measurements indicate that the band-gap energy of the GaN/PMMA composite is approximately 3.51 eV.