Site Selective Magneto-Optical Studies of Eu ions in Gallium Nitride

Abstract

We report site-selective studies of the Zeeman splittings that are observed for magnetic fields up to 6.6T for different Eu incorporation sites in GaN. Utilizing resonant excitation with visible light, we are able to distinguish the site and find for one center (Eu1) a splitting into five components as expected for C3v symmetry. The corresponding g-values are 1.66 and 1.90. The two lines of another center Eu2 each split into two levels corresponding to g-values of 1.9 and 2.84. Most surprisingly a third center, for which only one line is clearly identified, a g-value of 6.16 is found which is larger than can be explained for a 7F2 purely ionic Eu state.

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.…”

Charge state of vacancy defects in Eu-doped GaN

“…In addition, two other studies on the properties of the luminescence from GaN:Eu under the application of a magnetic field showed that OMVPE8 exhibited a curiously large effective g-factor of ~6, which was estimated by analyzing the Zeeman splitting of the emission peaks. [34,35] This is much larger than the effective g-factor measured for the other Eu centers, which ranged from ~1.9 -2.6. Neither of the studies offered an explanation as to the mechanism behind the large effective g-factor.…”

“…Interaction with the crystal field will cause the measured g-factor to deviate from this value, as can be seen from the previously reported effective g-factors of Eu1 (~1.8 -2). [34,35] The effective g-factors obtained from the emission spectra in Figure 4 are 2.8 and 6.1 for Eu2 and Eu2*, respectively. While these values are within reasonable agreement with those previously reported, [34,35] it remains that these effective g-factors, especially from Eu2*, are comparatively high.…”

“…[34,35] The effective g-factors obtained from the emission spectra in Figure 4 are 2.8 and 6.1 for Eu2 and Eu2*, respectively. While these values are within reasonable agreement with those previously reported, [34,35] it remains that these effective g-factors, especially from Eu2*, are comparatively high. The unusually large effective g-factor measured for the 2.007 eV emission line of Eu2* (~6.1) indicates that this transition is related to a state with a higher spin than would be expected for an isolated Eu 3+ center.…”

“…While similar experiments have been performed on GaN:Eu, it is necessary to confirm these results on the samples used in this study. [34,35] Since the sample with a V/III ratio of 6400 shows more Eu2 and Eu2* emission, it should be easier to compare the effective g-factors obtained from the Zeeman splitting of their brightest emission lines. This observation results from the splitting of the 7 F 2 multiplet, since the 5 D 0 should not split due to the magnetic field.…”