Halide vapor phase epitaxy (HVPE) is the most promising method for obtaining bulk GaN, and a 2 inch free standing wafer has been already obtained by growing on a sapphire substrate and separating by laser irradiation. It is, however, neither very easy nor very productive. Here we propose another more productive way of growing on GaAs substrate, though a free standing GaN is not yet perfectly obtained. It was found that hexagonal GaN with a smooth surface can be grown on GaAs (111) substrates at as high as 1000 by introducing GaN layer grown at an intermediate temperature such as 850. Surface of the GaN layer grown at 850 was rough but it became smooth surface when GaN was grown on it at 1000, though sometimes there were several hexagonal pits on the surface. The θ-2θ and ω X ray diffraction (XRD) of the grown layer showed only hexagonal GaN(0002).