Combined Excitation Emission Spectroscopy (CEES) of RE Ions in Gallium Nitride

Abstract

We review the results of site-selective spectroscopy studies of REdoped III-nitrides performed using combined excitation emission spectroscopy (CEES). This systematic technique allows the identification of a large number of different incorporation sites for three RE dopants (Eu, Er, Nd) in GaN. The technique is ideally suited to distinguish different sites from additional lines that are caused by thermally activated levels or phonon-assisted transitions. In this way, we reassign spectra in a new consistent manner. Utilizing the spectral fingerprints of each different site, we show how the relative occupation of sites is influenced by the growth and doping conditions. For Er³⁺ we characterize how the sites participate in up-conversion excitation processes. For Eu3+ we are able to relate the sites to different excitation channels after above-bandgap excitation.