Post-growth annealing and electron beam irradiation during cathodoluminescence were used to determine the chemical origin of the main optical emission lines in moderately and heavily Mg-doped GaN. The 3.27eV donor-acceptor pair (DAP) emission line that dominates the emission spectrum in moderately Mg-doped (p-type) GaN was found to be strongly reduced by electron irradiation and of different chemical origin than the DAP at a similar energetic position in Si-doped (n-type) GaN. These results suggested that the acceptor responsible for the 3.27eV DAP emission in Mg-doped GaN was Mg and that the donor (20–30meV) was H-related, possibly a (VN-H) complex. This complex was dissociated either by electron irradiation or thermal annealing in N2 or O2 atmosphere. It was found that upon electron irradiation, a deeper emission line (centered at 3.14eV) emerged, which was assigned to a DAP consisting of the same Mg acceptor level and a deeper donor (100–200meV) with a similar capture cross section as the donor in the 3.27eV emission. Moreover, 2 different deep donor levels at 0.35 and 0.44eV were identified as being responsible for the blue band (2.8–3.0eV) in heavily Mg-doped GaN. The donor level at 350meV was strongly affected by electron irradiation and attributed to a H-related defect.

Dissociation of H-Related Defect Complexes in Mg-Doped GaN. O.Gelhausen, M.R.Phillips, E.M.Goldys, T.Paskova, B.Monemar, M.Strassburg, A.Hoffmann: Physical Review B, 2004, 69[12], 125210 (9pp)