Excitation pathways and efficiency of Eu ions in GaN by site-selective spectroscopy

Current status for light-emitting diode with Eu-doped GaN active layer grown by MBE

“…Some of these weak peaks, labelled as A 0 , B 0 , and C 0 , have an energy shift of 10 meV from the corresponding major peaks. This energy shift agrees well with the localized phonon energy of Eu in GaN [22][23][24]. The energy difference between peak A 00 and peak A is about 63 meV, which is very close to the phonon energy for A 1 (TO) and/or E 1 (TO) in GaN [24].…”

“…There are at least two types of major optically active Eu 3 þ sites as reported previously [23,[26][27][28][29][30][31]. One of them has the emission wavelength of 620 nm and can only be excited by the above bandgap excitation.…”

“…The other one has the emission wavelength of 622 nm and can excite by both the above and the below band-gap excitation. By comparing the wavelength and the excitation path, site-A and site-B are categorized as a deep trap and shallow trap excitation pathways, respectively [23]. Thus we can conclude that the local structure around optically active Eu 3 þ ions is affected by the Mg co-doping.…”

Eu3+ luminescence properties of Eu- and Mg-codoped AlGaN

“…Therefore, the use of AlGaN with larger bandgap is promising to improve the luminescence efficiency. On the other hand, several emission peaks were observed in the Eu luminescence in GaN corresponding to optical sites [18][19][20][21][22]. From combined excitation-emission spectroscopy (CEES), it was clarified that each optical site in GaN has a different excitation and emission efficiency [19].…”

Enhanced photo/electroluminescence properties of Eu-doped GaN through optimization of the growth temperature and Eu related defect environment

“…Details about this technique can be found elsewhere. 9,18 Resonant excitation gives information on the local environments of the various Eu centers, while indirect excitation gives information on the ability of each Eu center to acquire energy from the GaN host, and is similar to the process by which Eu ions are excited during current injection.…”