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Abstract: We have investigated the thermal stability of GaN powders using DTA–TG, XRD, and XPS. GaN powders have been treated below 1400°C in the flowing stream of N2 gas. The pure GaN powders is indecomposable below 1120°C, but annealing at 1050°C results in the degradation of the crystalline quality of the GaN powders. With the increase of the temperature, more and more GaN powders are separated into Ga metal in the temperature range of 1120–1312°C, but the decomposition of GaN is propitious to improvement of the crystalline quality of GaN. When the temperature exceeds 1312°C, all the GaN powders are converted into Ga metal. The morphology of the samples obtained in the different temperature regimes was investigated using SEM. The results indicate that the average size of the samples obtained at the decomposition temperature regimes of the GaN powders is bigger. [Copyright &y& Elsevier]

Abstract: Amorphous GaN (a-GaN) films on Si (111) substrates have been deposited by RF magnetron sputtering with GaN powder target. The growth process from amorphous GaN to polycrystalline GaN is studied by XRD, SEM, PL and Raman. XRD data mean that annealing under flowing ammonia at 850–950°C for 10min converts a-GaN into polycrystalline GaN (p-GaN). The growth mechanism can be mostly reaction process through N3− in amorphous GaN replaced by N3− of NH3. Annealing at 1000°C, the appearance of GaN nanowires can be understood based on the vapor–liquid–solid (VLS) mechanism. In addition, XRD, PL and Raman measurement results indicate that the quality of GaN films increases with increasing temperature. The tensile stress in the films obtained at 1000°C is attributable to the expansion mismatch between GaN and Si, with the gallium in the film playing a negligible role. [Copyright &y& Elsevier]