Effects of self-induced negative bias in radio-frequency (rf) sputtering on the structure of the deposited film are discussed on the basis of the measured characteristics of the gallium nitride (GaN) films. A powdered GaN target was sputtered by either argon (Ar) or nitrogen (N-2) gas to investigate the effects of the sputtering. When sputtering with Ar gas, the resputtering due to the ion bombardments produces a film deficient in nitrogen with poor crystallinity. The ion bombardment eventually destroys the crystal structure producing a black amorphous film caused by gallium atoms forming clusters. Alternatively, when sputtering with N-2 gas, the activated nitrogen atmosphere enhances nitrogen incorporation and prevents the destruction of the crystal structure, making the film stoichiometric. To obtain high crystallinity, the effect of the self-induced negative bias should be minimized by decreasing the rf power and increasing the total pressure. (c) 2006 American Vacuum Society.