Observation of a Be-correlated donor state in GaN

A Be-related donor level was identified in the band gap of GaN. Thermal admittance spectroscopy (TAS) was combined with the radiotracer principle by applying the radioactive isotope 7Be which was implanted into n-type and p-type GaN. TAS spectra of n-type GaN recorded, repeatedly, during the elemental transmutation of 7Be to 7Li reveal one shallow donor level undergoing concentration changes correlated to the radioactive decay (7Be→7Li;T1/2=53.3d). From this, a relation is deduced between Be and this level at 390 meV below the conduction band edge of GaN. Furthermore, the implantation of 7Be was observed to enhance the hole concentration significantly in Mg-doped p-type GaN. A Be-correlated acceptor state was not detected.