Hydrazine has been used as a nitrogen source for the organometallic vapor phase deposition of GaN using trimethylgallium and a nitrogen carrier gas in the temperature range 425-960°C. Hydrazine and trimethylgallium form an adduct at room temperature which decomposes over the substrate with an activation energy of 1 eV for temperatures below 650°C. No carbon has been detected by Auger spectroscopy in the films. The electrical properties are dominated by oxygen impurities, probably originating from the hydrazine. Since hydrazine readily decomposes above 400°C, it is a better source of nitrogen for low-temperature depositions than other, more stable nitrogen sources.