We have investigated the growth of crack-free AlxGa1-xN layer (0.133 greater than or equal to x > 0.1) with low dislocation density using AlxGa1-xN/GaN heterostructure. From the wet-etched surfaces and transmission electron microscopy (TEM) images, the 2 mum underlying AlxGa1-xN layer with low AIN molar fraction is effective in preventing the formation of cracks in AlxGa1-xN surface. Although the number of defects in the underlying AlxGa1-xN layer grown on low-temperature GaN buffer are increased by the increase of AIN molar fraction, the use of the highly strained AlxGa1-xN/GaN/AlxGa1-xN heterostructure on the underlying layer is effective in reducing the number of defects near the surface. The possibility of the growth of crack-free AlxGa1-xN/GaN heterostructure with low dislocation density by controlling the AIN molar fraction and the misfit strain value is presented.