Spectra and energy levels of Tb3+ (4f8) in GaN

The cathodoluminescence spectra of Tb3+ ions implanted and annealed in GaN epilayers have been analyzed and modeled according to its incorporation into a substitutional Ga lattice site having D-2 point group symmetry. High-resolution emission spectra obtained at 11 K between 380 and 750 nm are identified as transitions from the (5)G(6),D-5(3) combined manifold and the D-5(4) manifold to individual energy (Stark) levels of the F-7(J) multiplet manifolds. All intense peaks and nearly all weaker peaks and bands are associated with emission from Tb3+ ions in a similar site. The observed crystal-field splitting of the F-7(6),F-7(5), and F-7(4) manifolds is much too large for any lattice-sum predictions based on Tb3+ ions in C-3v sites. Calculated splittings and relative intensities based on a site symmetry of D-2 give the best overall agreement with the observed data. (C) 2002 American Institute of Physics.