Deep Levels in GaN

Abstract

Deep levels in GaN are summarized. E1 and E3 electron traps at the respective energies of around EC − 0.25 eV and EC − 0.6 eV have been commonly observed in n-type GaN layers. H1 hole trap at around EV + 0.9 eV is reported in both n-type and p-type GaN layers, and likely associates the yellow luminescence band in a photoluminescence spectrum. The concentration of Ha hole trap at around EV + 0.3 eV in p-type GaN layers is detected with a nearly equal concentration of H1 hole trap. Based on the comparison with the first-principles calculations using hybrid functionals and the photoluminescence studies, the origins of E3, H1 and Ha traps are most likely attributed to 0/- charged state of iron on Ga site (FeGa), 0/− and +/0 charged states of carbon on nitrogen site (CN), respectively. Among deep levels induced by irradiation, EE1 and EE2 at around EC − 0.12 eV and EC − 1 eV correspond to the calculated energy levels of the nitrogen vacancy (VN) and the interstitial (NI). Finally, deep levels compensating carriers in n-type and p-type GaN layers are extracted.