Ammonia thermally treated gallium nitride deposited on gold-nucleation sites

The structural and optical properties of gold-nucleated GaN grown on Au/Si (100) and Au/c-sapphire were enhanced using a post-annealing procedure at 950 °C, under an ammonia environment. Before the GaN chemical vapor deposition process, the formation of Au droplets was promoted by an in situ dewetting mechanism, applying a heat treatment to the Au-covered c-sapphire, and silicon (100) substrates. The size and morphology of the Au sites were characterized by atomic force microscopy. According to the X-ray diffraction and Raman spectroscopy results, crystalline enhancement of the GaN wurtzite structure was obtained in both, the Au/sapphire and Au/Si (100). SEM micrographs reveal the presence of GaN micro-whiskers in as-grown samples. After the treatment herein proposed, morphology was modified as shown in the plan-view and cross section results. The GaN near-band emission at 3.34 eV was boosted by the localized surface plasmon effect. Additionally, the GaN bandgap energy was estimated by diffuse reflectance measurements and by the modified Kubelka–Munk function, as 3.35 eV.