Nature and excitation mechanism of the emission-dominating minority Eu-center in GaN grown by organometallic vapor-phase epitaxy

In-situ doped Eu ions in GaN grown by Organometallic Vapor-phase Epitaxy (OMVPE) at different pressures were investigated under different excitation methods and through the use of the following experimental techniques: (1) resonant site-selective laser irradiation (2) electron beam excitation, and (3) a dual excitation using a combination of electron beam and laser irradiation. With these means, we have examined the difference in the excitation pathways that result from resonant laser and electron hole (e-h) pair excitation of Eu ions for two different distinct incorporation sites, which are responsible for most of the luminescence. We have obtained clear evidence that e-h pairs do not have the ability to excite all of the ions and that there is excitation trapping by defects involved in the Eu excitation.