“…It is expected that Yb 3+ ions in GaN should have only seven 4f electrons energy levels due to the Yb 3+ ions occupying sites of C3 v symmetry: four levels of the ground 2 F 7/2 multiplet and three levels of the excited 2 F 5/2 multiplets, respectively. By investigating the low temperature high resolution PL and CL spectra of Yb-doped GaN, we have established an experimental energy level diagram in our recent work [23]. However, many lines detected in near infrared spectral region could not be associated with Yb 3+ ions occupying substitutional Ga 3+ ion sites.…”