| AVS 59th Annual International Symposium and Exhibition | |
| Actinides and Rare Earths Focus Topic | Monday Sessions |
| Session AC+TF+SS+MI-MoA |
| Session: | Actinides and Rare Earths: Thin Films and Surface Science |
| Presenter: | K.P. O'Donnell, Strathclyde University, Scotland, UK |
| Authors: | K.P. O'Donnell, Strathclyde University, Scotland, UK P.R. Edwards, Strathclyde University, Scotland, UK R.W. Martin, Strathclyde University, Scotland, UK K. Lorenz, ITN Sacavém, Portugal E. Alves, ITN Sacavém, Portugal V. Darakchieva, ITN Sacavém, Portugal M. Bockowski, Unipress, Poland |
| Correspondent: | Click to Email |
Europium-doped p-type GaN shows spectral switching and luminescence hysteresis when samples are temperature-cycled between room temperature and 20 K (K.P. O'Donnell et al, Late News paper at ICPS2012, Zurich). An explanation of this unusual behaviour may be found in the charge-state dependence of the local structure of the Mg acceptor in GaN, recently modelled by J.L. Lyons et al., (Phys. Rev. Lett. 108, 156403 (2012)). Eu ions, sensitive to their local environment, may act as 'spectators' of the charge-induced local distortions. The dominant impurity-induced luminescence spectrum at RT (hereafter, Eu0) switches completely to another spectrum (Eu1) when samples are cooled below 25 K. Upon subsequent warming of the sample, Eu1 fades with increasing temperature, as expected, but Eu0 does not reappear until the temperature exceeds 150 K; its recovery is complete only above 210 K. The noted temperature extremes correspond to hole localisation (carrier freeze-out) and delocalisation, respectively. Here, we extend Lyons' model to consider the possibility of observing the resonance in which the acceptor alternates rapidly between neutral and negative charge states, leading to a spatial oscillation of the associated defect between Eu0 and Eu1 forms, and describe the possible spectral identification of this resonance.