Nowadays, it has been proved that Gallium Nitride-based (GaN-based) semiconductor material has potential for the commercial applications to the backlight module of LCD, optical storage system, high frequency and high power microwave electronic device, and so on. As to the epitaxial growth of GaN-based semiconductor material, sapphire substrate is mainly used as substrate.
However, it is a main topic to reduce production cost and to improve film quality in the application of lighting and electronic devices, and therefore, silicon substrate tends to be utilized for cost down. Nevertheless, the derivational issue is the mismatch between nitride and silicon in lattice constant and thermal expansion coefficient, and thus it may cause GaN epitaxial layer to have considerable cracks and tensile stress. Accordingly, the yield of large-size GaN epitaxial chip is too low to reduce production cost.