Morphological and optical characterization of GaN prepared by pulsed laser deposition

GaN films were grown by pulsed laser deposition (PLD) on different crystalline substrates using a KrF excimer laser to ablate a hexagonal phase GaN target in a reactive atmosphere of ammonia. Films with small homogeneously distributed granular structures over the entire sample surface were obtained. The microstructure and surface morphology of the deposited layers were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and Raman spectroscopy (RS). XRD reveals that the structure of the GaN layer is predominantly wurtzite. AFM images reveal that all the deposited layers have a relatively smooth surface, while RS confirmed the predominant presence of hexagonal GaN with a high polycrystalline character. Analysis of the results obtained for samples grown under different conditions, such as the substrate temperatures in the growth chamber as well as different substrates used, helps to define better the experimental conditions of the growth process of PLD-GaN films.