Spin resonance investigations of GaN and AlGaN

Electron Spin Resonance (ESR) and related methods have been used to study defects in GaN and in Al_xGa_1-xN ternary alloys. In particular, Light-induced ESR of a thick MOCVD grown layer of GaN shows that the ESR signature of the deep defect appears for excitation energies > 2.6 eV and saturates above 2.7 eV. This information provides a direct measure of the energetic level position of the diamagnetic to paramagnetic transition of this center. Furthermore, standard ESR investigations of MBE-grown layers of Al_xGa_1-xN alloys were performed with emphasis on the effective-mass donor resonance. Composition and temperature-dependent measurements of the resonance position are presented.