A secondary-ion mass spectroscopic study of a wurtzite GaN(0001) surface was conducted to test the operation of a novel surface-chemical analyzer using Ar³⁺ (7.5 keV) and Ar⁴⁺ (10 keV) ions. The analyzer allows us to measure the time of flight of a secondary ion simultaneously with the detection of the backscattered atom or ion that captured electrons from the surface atoms. A proton, C_mH_n⁺ (m = 1—6 and n = 0—13), N⁺, Ga⁺, and GaN⁺ ions were observed in the mass spectrum. The spectral width and profile were different between Ar⁰ and Ar⁺ -coincidence measurements. [DOI: 10.1380/ejssnt.2009.21]