Emission enhancement mechanism of GaN:Eu by Mg codoping

Abstract

Mg codoping into Eu-doped GaN strongly affects the two dominant optical sites A (620.3 nm) and B (622.3 nm) and dramatically improves the optical characteristics obtained from Eu 3þ ions. To clarify the mechanism of the enhanced emission, the effects of the Mg concentration on the excitation and emission processes were evaluated by considering the excitation power dependence of photoluminescence (PL) and time-resolved PL at various temperatures. The excitation cross section r ex , which reflected the excitation process, did not depend on the Mg concentration but strongly on the optical site, which was attributed to the different energy transfer processes of the two optical sites. r ex for site A was three times larger than that for site B, indicating higher excitation efficiency for site A. Mg codoping dramatically increased the number of Eu ions in site A that remain active at room temperature (RT) and the 5 D 0 lifetime at RT, indicating the suppression of nonradiative components during the emission process. Therefore, the optical properties were markedly enhanced by Mg codoping. V C 2013 American Institute of Physics. [http://dx.

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

“…The excitation cross section did not depend on N Mg , for any of the optical sites (not shown), indicating that Mg codoping did not influence excitation efficiency. The excitation cross section for site A was larger than that for site B, which is in good agreement with other reports on GaN:Eu fabricated by ion implantation and GaN: (Eu, Mg) grown by MBE [20,25].…”

“…The PL decay time at RT increased from 51 to 164 μs with increasing N Mg , which suggested that Mg codoping was effective to reduce the nonradiative component resulting from the backtransfer process; that is, Mg codoping might contribute to decrease the native or unwanted defect in the AlGaN host as well as GaN [25].…”

“…For Er-doped GaAs, oxygen codoping facilitated the formation of a specific local structure and resulted in the unification of the emission peak [23]. We developed an Mg-codoping technique for GaN:Eu grown by NH 3 -source MBE, which achieved the selective activation of one site and enhancement of PL intensity from Eu ions at RT [24,25]. The improvement of optical properties by Mg codoping has also been reported for OMVPEgrown Eu-and Mg-codoped GaN (GaN:(Eu, Mg)) and Eu-implanted Mg-doped GaN [26,27].…”

Self-Organized Eu-Doped GaN Nanocolumn Light-Emitting Diode Grown by RF-Molecular-Beam Epitaxy

“…First, to understand the effect of Eu concentration on the transfer efficiency, σ ex at 25 K as a function of Eu concentration is shown in Figure . σ ex was almost constant at 1 × 10 −16 –4 × 10 −16 cm 2 , which is consistent with that of GaN:Eu thin film fabricated by ion implantation or grown by RF‐MBE in previous reports, even at a concentration higher than that at which concentration quenching was observed. This indicated that the transfer efficiency from GaN to Eu ion was not affected by the Eu concentration.…”

The role of donor-acceptor pairs in the excitation of Eu-ions in GaN:Eu epitaxial layers

“…[1][2][3][4] While the optical and magneto-optical properties of this system have been extensively studied, information on the nature and structure of the incorporation environments of Eu in GaN is still incomplete. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] In early samples, as many as eight incorporation sites have been identified in GaN:Eu, grown by organometallic vapor-phase epitaxy (OMVPE). 17 However, it has been determined that two of these sites, commonly referred to as Eu1 and Eu2, represent roughly 85-95% of the overall Eu incorporation in GaN, and play the largest role in the luminescence properties of the system.…”