Electron trapping effects in C- and Fe-doped GaN and AlGaN

Iron- and carbon-doped GaN and iron-doped Al0.2Ga0.8N irradiated by low energy electron beam of scanning electron microscope were studied by cathodoluminescence and electron beam-induced current techniques. Irradiation is 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 yielded activation energies for irradiation-induced effects of 210, 230, and 360 meV for GaN:C, GaN:Fe, and Al0.2Ga0.8N:Fe, respectively. These observations are consistent with trapping of non-equilibrium electrons on deep, non-ionized acceptor levels.