Passivating films were grown on gallium arsenide by direct nitridation with hydrazine at 300-400-degrees-C. Auger electron spectroscopy and x-ray photoelectron spectroscopy analysis show that the films are primarily gallium nitride with an oxide impurity. The oxide content is a function of the surface pretreatment, reaction temperature, and water concentration in the hydrazine. Improvements in the band gap photoluminescence with nitridation indicate a lower surface state density and reflect an improvement in the termination of the semiconductor lattice.