One Be-related donor level in the band gap of GaN was identified by Radiotracer Deep Level Transient Spectroscopy (DLTS) and Thermal Admittance Spectroscopy (TAS). The radioactive isotope Be-7 was implanted into n-type GaN for these experiments. DLTS and TAS spectra were recorded, repeatedly, during the elemental transmutation of Be-7 to Li-7, whereof the TAS spectra exhibit one level Undergoing correlated concentration changes. From this, a relation is deduced between this level at 390 meV below the conduction band edge and a Be-correlated donor state in GaN. Furthermore, the implantation of Be-7 into Mg-doped p-type GaN was observed to enhance the hole concentration significantly. DLTS spectra taken at n-GaN implanted with the radioactive isotope Mg-28 show time-dependent concentration changes that are not related to the characteristic time of the radioactive decay.