“…AlN has wide band gap (6.2 eV), high breakdown voltage high thermal conductivity, good acoustic velocity, high dielectric constant (8.5), high hardness, and high wear resistance, which make it suitable for various applications [1,2] , such as optoelectronic devices (especially in the UV region), high power and high temperature applications, surface acoustic wave devices, dielectric alternatives to SiO 2 for MOSFETs, hard films and optical films, etc. Moreover, AlN thin film can be used as a buffer layer to solve the mismatch problems existed in the epitaxial growth of some wide band gap materials on Si or sapphire substrates [3] .…”