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We study the growth of AlxGa1-x N epilayers on (0001) sapphire by low-pressure MOCVD, using a low-temperature A1N buffer. By varying the input now rates of trimethylgallium (TMGa),e obtain crack-free AlGaN films in the whole range of composition. A linear relationship between gas and solid Al content is observed. The structural properties of the layers (x = 0 - 1) are investigated by x-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM).It is found that a two-direction growth appears along the c-axis and the (10(1)1) directions for x≥0.45.From the results of Raman spectroscopy, we suggest that the compressive stain and the lack of mobility of Al adatoms can induce the formation of (1011) grains.