Optical studies and crystal field calculation of GaN nanorods doped with Yb3+ ions

Optical properties of Yb-doped GaN single crystalline nanorods (NRs) grown by molecular beam epitaxy (MBE) under different growth conditions on silicon (1 1 1) substrates were investigated. High resolution scanning electron microscopy (HRSEM) was used to study the shape and size of GaN:Yb3+ NRs which are found to be about 25 nm diameter and 300-500 nm long. The low temperature cathodoluminescence spectra (CL) of GaN:Yb3+ NRs were examined. The GaN:Yb3+ NRs CL spectra show visible broad emission due to GaN host defects and near infrared emission associated with Yb3+ ions. Comparative investigations of the luminescent properties of GaN:Yb3+ NRs with those of GaN:Yb3+ thin films show the presence of some similarities between the lattice locations of Yb3+ ions in these hosts with a broadening of the emission lines which can be explained by the defect surface effect. Assuming the presence of two sites occupied by Yb3+ ions, the majority of CL emission lines was attributed. The experimental Stark energy levels of the two Yb3+ ion manifolds are established for the Yb-doped GaN NRs.