Site Multiplicity of Rare Earth Ions in Iii-Nitrides

Abstract

This presentation reviews recent lattice location studies of rare earth (RE) ions in GaN by electron emission channelling (EC) and X-ray absorption fine structure (XAFS) techniques. These studies agree that RE ions at low concentrations (whether they are incorporated during growth or introduced later by ion implantation) predominantly occupy Ga substitutional sites, as expected from considerations of charge equivalence. We combine this result with some examples of the well-documented richness of optical spectra of GaN:RE 3+ to suggest that the luminescence of these materials may be ascribed to a family of rather similar sites, all of which feature the RE Ga defect.

Selectively excited photoluminescence from Eu-implanted GaN

“…It is interesting to note further that PL spectra of luminescent Eu:GaN samples generally show a set of near-band-edge luminescence peaks in the wavelength range from 370 nm to 400 nm. 12 Figure 1͑b͒ confirms that the PL spectrum excited below the bandgap is markedly different from the spectrum excited at 356 nm. The line at 620.8 nm is now the weakest of the four and the peak at 622.5 nm is enhanced.…”

“…Temperature dependent measurements show different thermal quenching behavior for the three peaks in our previous work, 12 and also consistent with the results in the report by Nyein et al 8 We have also investigated selectively excited PL in the regions near 664 nm ͑ 5 D 0 -7 F 3 ͒ and 602 nm ͑ 5 D 0 -7 F 1 ͒ and seen effects similar to those for 5 D 0 -7 F 2 , with the relative strength of the lines within the observed multiplets strongly modified when the excitation energy is changed from above to below the GaN band gap.…”

Optical properties of high-temperature annealed Eu-implanted GaN

“…PL and PLE spectroscopy has been carried out from 15 to 297 K. Temperature dependent measurements demonstrate different thermal quenching rates for the three main peaks excited by He-Cd laser at 325 m in our previous work [13]. The PL peak at 620.8 nm quenches much faster than the other two peaks when the sample is excited above band gap.…”

“…Hence, only the line pair at 621.7 and 622.5 nm is excited in the broad band. It is interesting to note further that PL spectra of luminescent Eu:GaN samples generally show a set of near-band-edge luminescence peaks in the wavelength range from 370 to 400 nm [13]. Fig.…”

Rare earth doped III-nitrides for optoelectronics

“…An abbreviated early version of this review was presented at the Fall Meeting of the Materials Research Society in December 2004 and was subsequently published in the Proceedings of that Symposium [9].…”