Crystal field and Zeeman parameters of substitutional Yb3+ ion in GaN

Cathodoluminescence (CL) and photoluminescence (PL) spectra of GaN grown by metalorganic chemical vapor deposition on (0 0 0 1) sapphire substrate and doped by implantation with ytterbium ions (Yb3+) were critically examined. We report on the crystal field (CF) energy levels calculation of Yb3+ ions in GaN host using CF theory. The CL and PL spectra are interpreted in terms of lattice-sum and crystal-field splitting model assuming that implanted Yb3+ ions replace substitutionally Ga cation in a single site (YbGa) and that YbGa are associated with nitrogen vacancy in a complex defect center (VN–Yb). We demonstrate that assuming the existence of these two centers, good agreement between measured and calculated energy levels of Yb3+ ion transition lines can be obtained. Careful analysis of the available experimental results revealed that transition lines assigned to VN–Yb defect center overlap with the emission lines originating from the intrinsic Fe3+ ion in the GaN host. Implications of this evidence on the developed Yb3+ ion energy level diagram and modeling of the Yb-doped GaN spectra are critically reviewed. Furthermore, on the basis of the derived wave functions, the Zeeman g|| and g⊥ parameters for Yb3+ ion in a Ga substitutional sites are calculated. This center is characterized by g-values of |g||| = 1.308 and |g⊥| = 3.135.