In this study, gallium nitride (GaN) nanowire (NW) arrays were grown on a gold-coated Si(111) substrate by metalorganic chemical vapor deposition (MOCVD). The important parameter that decides the density of GaN NWs was considered to be growth temperature. Therefore, in order to study the effect of growth temperature, we grew GaN NWs at various growth temperatures, namely, 800, 850, 900, 950, and 1000 C, under identical growth conditions. The optimum growth temperature was observed to be 950 C, and the diameters of the grown GaN NWs were in the range from 80 to 250 nm, and the average length was 3 mm. The surface morphology and optical characterization of the grown GaN NWs were studied by field emission scanning electron microscope (FE-SEM), photoluminescence (PL), and cathodoluminescence (CL), respectively. Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of gallium and nitrogen in the grown NWs. The PL and CL spectra revealed sharp peaks at 366 nm with a full width at half maximum (FWHM) of 102 meV and at 3.36 eV with a FWHM of 85 meV, respectively, indicating that the grown GaN NWs were highly crystalline.
InN nanocolumns were grown on a gold-coated Si(111) substrate by metal-organic chemical vapor deposition (MOCVD). Herein, indium predeposition was performed before InN nanocolumn growth. The InN nanocolumns were obtained by forming Au+In solid solution droplets on the Au-coated substrate and subsequently nitriding these droplets. In this study, we investigated the morphological properties of InN nanocolumns by changing the growth conditions such as growth temperature, trimethylindium (TMI) flow rate, and growth pressure. Scanning electron microscopy (SEM) showed that the InN nanocolumns were hexagonal with diameters ranging from 90 to 180 nm and a length of approximately 2.5 mm. The Raman spectrum of the InN nanocolumns showed peaks at 492 and 596 cm À1 , which were assigned to E 2 and A 1 longitudinal optical (LO) phonon modes of InN, respectively. From the high-resolution X-ray diffraction (HR-XRD) spectrum, the predominant diffraction pattern from the InN(101) plane was observed at 33.215 .
Vertical GaN nano-columns arrays were grown on Au-coated silicon (111) substrate by Au+Ga alloy seeding method and pulsed flow of Gallium and ammonia using metalorganic chemical vapor deposition (MOCVD). A gold thin film was deposited on Si using an ion coating system. The Au coated Si substrate was annealed at 800 oC under hydrogen ambient for 5 min. The pre-deposition of gallium and nitrogen was performed for 60 sec to form Au+Ga and nitrogen solid solution, which acts as the initial nucleation islands. Then Gallium and ammonia were let in pulse method. Scanning electron microscopy (SEM) image reveals a vertical growth and cylindrical in shape GaN nano-column. From the sharp PL peak intensity it is clearly seen that the dislocation density is reduced considerably and the optical quality of the nano-column is improved.
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