Photoluminescence studies and crystal field calculations of Yb-doped InGaN nanorods

We report on photoluminescence (PL) measurements of InGaN:Yb3+ nanorods (NRs) in combination with crystal field calculations. The observed near band edge (NBE) shift has been discussed in terms of its three possible factors: Indium content fluctuation, strain relaxation and quantum confinement. The transition lines between Stark energy levels of Yb3+ ion were detected and analyzed. Ytterbium ions were described as having similar lattice locations in InGaN and GaN NRs after a comparison between their luminescent properties. Consequently, we established the experimental energy levels for Yb3+ ion in InGaN NRs from the assignment of almost all the emission lines to YbGa substitutional site. The corresponding crystal field parameters were determined based on the observed Stark splitting of 4f manifolds. The In and Yb concentrations were calculated from the X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) reveal the single crystalline nature of the nanorods.