| Chemical equilibria analyses in the Ga/In-H-C-Cl-N-inert system were performed to predict gas and condensed phase species that might exist in H-MOVPE of GaN and InN. It was found that carbon co-deposition and metal droplets (Ga or In) formation can be eliminated by providing a threshold level of H 2 and HCl, respectively. The transitions between deposition and etching, and between 2-phase (Ga or In)N and pure (Ga or In) metal and single-phase (Ga or In)N were predicted as a function of N/III and Cl/III molar ratios and temperature.; Stress was measured by Raman spectroscopy in two GaN films (grown by MOCVD and H-MOVPE, respectively) on sapphire and a difference of 2 cm -1 in the E2 mode was observed. Subsequent measurement by XRD-SM, rocking-curves, AES, and SIMS showed inconsistent results compared to the Raman result suggesting that the Raman E2 shift may not be only related to biaxial or hydrostatic stress.; Controlled growth of InN nanorods (NR) was achieved by varying the Cl/In and N/In molar ratios and growth temperature. The NRs were grown on a, c, r-Al2O3, GaN/c-Al2O3, Si (100), and Si (111) without a template or external catalyst. Well-faceted wurtzite and threading dislocation-free NRs were observed by SEM and TEM. The diameters and lengths of nanorods ranged 100 to 300 nm and ∼ 1 mum for 1 hr growth. XRD patterns indicated the nanorods were textured in the [002] direction and TEM-DP confirmed the growth axis was predominantly [002]. Nanorods grown on GaN/c-Al2O3 occasionally showed vertical self-alignment and were epitaxially grown as judged by XRD pole-figure analysis. The nanorods had N-polarity as characterized by CBED, while RT PL showed a predominant peak at 1.08 eV. Raman spectroscopy showed three phonon lines (451, 496, and 596 cm-1) that were assigned to A1(TO), E22, and E1(LO), respectively. InN NRs-based gas sensor was fabricated that could detect H2 to 10 ppm.; Crack-free, 3 mum GaN films were grown on GaN/AlGaN/Si template at 850°C although cracks developed when the thickness exceeded 7 mum. It was possible, however, to grow crack-free polycrystalline 40 mum thick GaN on Si using InN NRs as a buffer material. |
