Effect of thermal annealing on luminescence properties of Eu,Mg-codoped GaN grown by organometallic vapor phase epitaxy

Abstract

The effects of thermal annealing on Eu,Mg-codoped GaN (GaN:Eu,Mg) grown by organometallic vapor phase epitaxy were investigated. After annealing in nitrogen ambient, Eu-Mg related photoluminescence emission was quenched to 13% without a change in the spectral shape. The quenched emission recovered to 65% of the original intensity after a subsequent annealing in ammonia ambient. Combined excitation emission spectroscopy and time-resolved photoluminescence results revealed that the quenching behavior is attributed to a nonradiative process induced by unpassivated Mg acceptors in the relaxation of excited 4f electrons of Eu ions.

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.…”

Vibrationally induced center reconfiguration in co-doped GaN:Eu, Mg epitaxial layers: Local hydrogen migration vs. activation of non-radiative channels

“…Analogous to what is well known for Mg-H centers in GaN, [3][4][5][6][7][8] these Eu related centers contain hydrogen as one of their components, which can be modified and removed by low energy electron-beam irradiation (LEEBI) and thermal annealing. [9][10][11][12][13][14][15][16][17] In the case of thermal annealing, at 800 C, for GaN:Eu, Mg, the overall emission intensity decreased, which was attributed to the opening of nonradiative traps local to the Mg. 17 LEEBI results in the modification of the Eu-Mg-V N -H centers, which is attributed to the electron-beam induced migration of the hydrogen, in the vicinity of the Mg, such that three different centers (labeled Mg/Eu1-3) could be identified. In the as-grown sample, the center labeled Mg/Eu1, for which the hydrogen sits in an interstitial position, is the most abundant (about 15% of the total number of Eu centers) but is converted to either Mg/Eu2 or Mg/Eu3 by low probe current LEEBI.…”

“…To determine the defect configuration after thermal annealing, the same samples as used in Ref. 17 were studied.…”

“…This will no longer be the case as we go to elevated temperatures and power densities. We will discuss the effect of these two factors individually, starting with the behavior under high temperature annealing, such as performed by Lee et al 17 They reported an overall decrease in intensity as well as a decrease in luminescence lifetimes of all Eu centers. The latter is most notable for Mg/Eu1 (Eu-Mg4 in Ref.…”

“…The latter is most notable for Mg/Eu1 (Eu-Mg4 in Ref. 17). We studied these samples using site-selective, resonant excitation, in order to determine the relative number of Mg/Eu 1-3 centers, before and after annealing.…”