Excitation of Eu3+ in gallium nitride epitaxial layers: Majority versus trap defect center.

We report studies of the excitation mechanism of Eu ions in situ doped during organometallic vapor-phase epitaxy (OMVPE) of GaN. We find that the bright red emission under above-band gap excitation originates primarily from an incorporation site that exhibits high excitation efficiency but occurs in low relative abundance (<3%). The latter represents a device efficiency bottleneck, limiting the emission at high excitation intensities. The majority site, which scales well with the total Eu concentration, exhibits low energy transfer efficiency but dominates the emission under direct excitation in the visible spectral region due to high relative abundance (>97%). [ABSTRACT FROM AUTHOR]