Physical Review B, 67(20), 205206 (2003)
C. D. Latham (a), R. M. Nieminen (a), C. J. Fall (b), R. Jones (b), S. Öberg (c), P. R. Briddon (d)
(a) Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, FIN-02015 HUT, Finland
(b) School of Physics, University of Exeter, Exeter, EX4 4QL, United Kingdom
(c) Department of Mathematics, University of Luleå, Luleå, SE-97187, Sweden
(d) Physics Centre, School of Natural Science, University of Newcastle upon Tyne, Newcastle NE1 7RU, United Kindom
(Received 6 September 2002; revised 8 November 2002; published 9 May 2003)
The properties of several point defects in hexagonal gallium nitride that can compensate beryllium shallow acceptors (BeGa) are calculated using the AIMPRO method based on local density functional theory. BeGa itself is predicted to have local vibrational modes (LVM's) very similar to magnesium acceptors. The highest frequency is about 663 cm-1. Consistent with other recent studies, we find that interstitial beryllium double donors and single-donor beryllium split interstitial pairs at gallium sites are very likely causes of compensation. The calculations predict that the split interstitial pairs possess three main LVM's at about 1041, 789, and 738 cm-1. Of these, the highest is very close to the experimental observation in Be-doped GaN. Although an oxygen donor at the nearest-neighboring site to a beryllium acceptor (BeGa-ON) is also a prime suspect among defects that are possibly responsible for compensation, its highest frequency is calculated to be about 699 cm-1 and hence is not related in any way to the observed center. Another mode for this defect is estimated to be about 523 cm-1 and is localized on the ON atom. These two vibrations of BeGa-ON are thus equivalent to those for the isolated substitutional centers perturbed by the presence of their impurity partners.
DOI: 10.1103/PhysRevB.67.205206
PACS: 61.72.Bb, 61.72.Ji, 61.72.Vv, 71.15.Nc
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