GaN is widely studied and developed as a material for new application in power electronics devices or as emitter of various color of light. GaN is usually formed by nitriding GaAs and grown on the sapphire substrate with a high dislocation density. For this dislocation, microchannel epitaxy (MCE) or regrowth of GaN is required to reduce dislocations. Recently, plasma treatment was used for interface treatment, regrowing of GaN crystal and nitridation process of GaAs. GaN surface was treated by atmospheric pressure microplasma using Ar and N2 as process gases and powered by AC and pulse power supplies. Modifications of the surface were observed after the treatment and they depend on the gas process, treatment time and power supply.