AlxGa1−xN GROWTH BY Si/N TREATMENT OF SAPPHIRE SUBSTRATE: COMPARISON WITH OTHERS GROWTH TECHNIQUES

AlxGa1−xN films were grown on Si/N-treated sapphire substrate by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) in a home-made vertical reactor. This process can be considered as randomly in situ epitaxial lateral overgrowth (ELO) technology. The growth firstly begins by three-dimensional (3D) mode and is completed in two-dimensional (2D) growth mode as shown by real time in situ laser (λ=632.8nm) reflectometry measurements and confirmed by scanning electron microscopy (SEM) images. Secondary ion mass spectroscopy (SIMS) measurements evidence Al composition pulling effect in the AlxGa1−xN layer. The Si/N treatment technique is compared to conventional AlxGa1−xN growth techniques. The results of high-resolution X-ray diffraction (HRXRD), photoluminescence (PL) measurements and SEM images agree well on the fact that the Si/N treatment produces AlxGa1−xN layers with comparable qualities of AlxGa1−xN layers grown on high temperature GaN template but with much higher qualities than AlxGa1−xN layers grown on low temperature AlN nucleation layer. Moreover, the Si/N treatment technique permits the growth of high quality AlxGa1−xN layers with appreciable thicknesses with respect to the others techniques.