<p>A method for preparing a GaN film material comprises: evaporating a metal nickel (Ni) film on a GaN/sapphire composite substrate, annealing to obtain nano Ni particles, then using an inductively coupled plasma etching (ICP) method to etch GaN on the GaN/sapphire composite substrate which is uncovered by Ni and forming a GaN/sapphire composite substrate with a nano structure. The hydride vapor phase epitaxy (HVPE) growth of GaN is carried out on the nano structure composite substrate to obtain a GaN film with low stress and high quality or a self-supporting GaN substrate material. The method of the invention can obtain the GaN film material with low stress and high quality.</p>
