We report on the results of the measurements of the low-frequency nitride/gallium aluminum nitride (GaN/GaAlN) heterojunctions grown on sapphire substrates. The noise spectra have the form of the1/fnoise with the Hooge parameter of approximately10−2.The effects of band-to-band and impurity illumination on the low-frequency noise show that the nature of the1/fnoise in GaN might be a result of the occupancy fluctuations of the tail states near the band edges. This mechanism of the1/fnoise is similar to that in GaAs and Si. ©1998 American Institute of Physics.