Crack-free and high-quality thick AlxGa1-xN, with x ranging from 0 to 1, has been grown on sapphire, using a low-temperature interlayer. The low-temperature AlN interlayer reduces tensile stress during the growth of AlxGa1-xN, while simultaneously improving the crystalline quality. The AlxGa1-xN film was characterized by high-resolution X-ray diffraction (XRD) and transmission electron microscopy (TEM).