Abstract
•GaN:Yb3+ NRs grown on different substrates are obtained by rf Plasma assisted MBE.•Optical characterization and crystal field calculation of GaN:Yb3+ NRs are established.•CL spectra of GaN:Yb3+ NRs show the presence of two main Yb3+ optical centers.•The effect of the nano structure on the Yb3+ optical centers was investigated.•The dominant Yb3+ optical center in the GaN NRs is the complex VN–Yb center.
Optical properties of Yb-doped GaN single crystalline nanorods (NRs) grown by molecular beam epitaxy (MBE) under different growth conditions on silicon (111) 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 25nm diameter and 300–500nm 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.