Studies of electron trapping in III-nitride semiconductors

Effects of electron irradiation on GaN and AlxGa(1-x)N doped with acceptor-forming species (Mg, C, Fe, and Mn) were studied by cathodoluminescence and electron beam induced current techniques. Low energy electron beam irradiation was shown to induce a systematic decay of the cathodoluminescence intensity, which is accompanied by increased electronic carrier diffusion length, indicating the increase of carrier lifetime. Temperature-dependent cathodoluminescence measurements allowed to estimate the activation energy for irradiation-induced effects, which was found to be comparable to the ionization energy of the dominant acceptor species. These observations are consistent with trapping of non-equilibrium electrons on deep, non-ionized acceptor levels. In (AI)GaN:Mg and GaN:C electrons are trapped by the ground state of the neutral acceptor atom, while in TM-doped compounds, electron irradiation-induced processes appear to involve a more energetically accessible excited states of the acceptors.