Total photoluminescence spectroscopy of GaN nanocrystals doped by Eu3+ ions

The purpose of this work was to investigate the optical properties of GaN nanocrystals (GaN-nc) doped by Eu3+ ions. The total photoluminescence excitation spectroscopy (TPLE) (where the full emission spectra were recorded for the different excitation wavelengths) has been performed to investigate the absorption properties and the energy transfer between GaN-nc and Eu3+ ions. Nanosized GaN: 1% Eu3+-nc with the average grain sizes of similar to 8 nm have been synthesized as a powder by the combustion method with some modifications. In PL spectra the strong emission lines related to Eu3+ ions have been observed with the most intense line at similar to 614 nm. Additionally, the broad yellow/red emission band related to GaN surface/defect states has been also observed. In recorded TPLE spectra an efficient excitation energy transfer from GaN-nc to Eu3+ has been observed. It has been shown that there are three channels for the excitation of Eu3+ ions: (i) through quantized states in GaN nanocrystals, (ii) through defect-related states in the GaN, (iii) and directly through the excited states of Eu+3 ions. It has been found that for investigated GaN powder the most efficient is the excitation of Eu+3 ions through quantized states in GaN nanocrystals.