Spectroscopic Analysis of Eu3+ Implanted and Annealed GaN Layers and Nanowires

A detailed spectroscopic analysis of Eu3+ implanted and annealed GaN nanowires (NWs) and layers is presented by using temperature-dependent steady-state photoluminescence, room temperature photoluminescence excitation, and time-resolved photoluminescence. Independently of the used implantation angle and ion fluence, all the studied postimplant annealed samples evidence red 5D0 → 7F J luminescence transitions of the Eu3+ (4f6) ions. One dominant Eu3+ optical center was found for both GaN NWs and layers, together with the presence of different overlapped Eu3+ minority optical centers. The thermal stability of the intra-4f6 lines was found to be higher for the NWs where the red emission is observed with the naked eye even at room temperature. Besides the lanthanide emission, the photoluminescence spectra of the NWs and layers exhibit a broad yellow luminescence band (YL) differing slightly in the spectral shape and peak position in the different samples. While the YL in the layers is commonly ascribed to a free to bound (e-A) or donor–acceptor pair (DAP) transitions, the recombination kinetics of the YL in the NWs supports a model for a surface-mediated recombination process.