Reactivation and passivation of theEc - 0.61 eV deep level in GaN

Abstract

Deep level transient spectroscopy (DLTS) measurements on as-grown GaN layers on sapphire substrates commonly reveal three dominant traps, viz. the 0.65 eV, 0.61 eV and 0.27 eV levels below the conduction band. These deep levels are normally attributed to the native defects that are present in the as-grown layers. We have previously observed that the Ec – 0.61 eV level behaves in an almost similar manner to bistable defects during bias-on/bias-off anneals. It is proposed that this is due to the presence of a negatively charged mobile species in the material that drifts under the influence of an electric field and is able to passivated the Ec – 0.61 eV level. Defect profiles of the level under zero bias and under different reverse bias conditions showed changes in the defect profile distributions that further confirms the mobile defect/ion theory. The reactivation kinetics of the Ec – 0.61 eV defect level has also been studied and results indicate that the energy required to reactivate the level is EReac = 0.96 ± 0.03 eV with an attempt frequency ν0 = 6 × 1010±1 s–1, while the reverse transformation of this level requires EPass = 0.93 ± 0.06 eV and an attempt frequency of ν0 = 7 × 1011±1 s–1. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)